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GENERAL 
AGRICULTURAL    CHEMISTRY 


BY 


Professor  ojf  Agricultural  Chemistry  in  the, 
University 


WILLIAM    E.    TOTTINGtlAM  ' 

Assistant  Professor  of  Agricultural  Chemistry  in  the 
University  of  Wisconsin 


MADISON,   WISCONSIN 
1913 


1913 


WILLIAM  -E.  TOTTINGHAM 


STATE  JOURNAL  PRINTING  COMPANY 

PRINTERS  AND  STKREOTYPKRS 

MADISON,  Wis. 


CONTENTS 

I     INTRODUCTION 7 

II    THE  ATMOSPHERE 24 

III     THE  SOIL  37 

IV     NATURAL  WATERS 74 

V    THE  PLANT 85 

VI     FARM  MANURE  118 

VII  COMMERCIAL   FERTILIZERS    155 

VIII  CROPS   182 

IX    THE  ANIMAL  BODY  216 

X     FEEDING  STANDARDS 239 

XI     FOOD  REQUIREMENTS  OF  ANIMALS 259 

XII     MILK  AND  ITS  PRODUCTS  278 

XIII     INSECTICIDES  AND  RELATED  SUBSTANCES 305 

APPENDIX  325 

INDEX   337 


PREFACE 

Since  the  time  of  Boussingault  and  Liebig,  agriculture  in  its 
many  phases  has  profited  from  the  science  of  chemistry.  A  store 
of  useful  information  has  been  made  available  through  the  study 
of  the  elements  and  compounds  fundamentally  concerned  in  the 
art  of  agriculture.  It  is  reasonable  to  expect  that  this  art  will 
in  the  future  be  enriched  from  the  same  source. 

This  little  book  was  written  in  the  interest  of  the  young  farmer 
and  the  student  beginning  the  study  of  agricultural  chemistry. 
No  extended  knowledge  of  chemistry  is  required  for  its  under- 
standing. It  makes  no  special  appeal  to  the  chemist.  It  is  a 
survey  of  the  general  field  of  chemistry  applied  to  agriculture, 
with  the  emphasis  placed  on  the  applied  side. 

Throughout  the  book  we  have  striven  to  express  safe  views 
rather  than  to  echo  the  most  recent.  Hypotheses  and  theories 
have  not  been  discussed  in  detail.  We  have  attempted  to  give, 
in  general,  only  well  tested  and  established  principles.  For  stu- 
dents who  have  had  some  chemical  training,  a  certain  amount  of 
formulation  has  been  introduced.  While  we  recognize  its  help- 
fulness, nevertheless,  it  is  not  essential  to  the  understanding  of 
the  main  facts  of  this  book. 

The  authors  have  drawn  freely  from  various  publications,  en- 
deavoring to  bring  together  from  scattered  sources  the  materials 
essential  to  such  a  work  on  agricultural  chemistry.  In  this  re- 
gard we  are  especially  indebted  to  the  works  of  Ingle,  Warington, 
Storer,  Voorhees,  Vivian,  Jordan  and  others,  all  of  which  have 
aided  greatly  in  the  preparation  of  this  work. 


CHAPTER  I 

INTRODUCTION 

Agricultural  chemistry  concerns  itself  with  the  chemical  com- 
position of  the  food  of  plants  and  animals  and  with  the  chemical 
changes  involved  in  the  processes  of  life.  It  has  to  deal  with  the 
composition  of  soil,  air,  and  water,  of  the  bodies  of  plants  and 
animals,  of  manures  and  commercial  fertilizers  and  with  the 
chemical  changes  which  these  substances  undergo. 

Before  beginning  the  study  of  the  soil  or  air  or  the  plant  it 
will  be  necessary  for  the  student  to  learn  something  of  the  im- 
portant elements  concerned  in  agriculture  and  the  meaning  of 
some  of  the  common  terms  used  in  chemistry. 

The  Avhole  earth,  so  far  as  is  known,  is  made  up  of  about 
eighty -one  elements,  a  large  proportion  of  which  play  little  or 
no  part  in  the  ordinary  processes  of  plant  and  animal  life.  In- 
deed a  considerable  proportion  are  found  only  in  extremely  small 
quantities  and  are  but  curiosities  to  the  student  of  chemistry. 
From  the  standpoint  of  the  farmer  they  possess  no  interest.  They 
are  called  elements  for  the  reason  that  they  are  the  simplest  sub- 
stances known,  and  cannot  by  any  means  yet  discovered,  be  sep- 
arated into  simpler  or  different  substances.  Iron,  gold,  silver, 
zinc,  lead,  and  sulphur  are  examples  of  elements. 

The  bodies  of  plants  and  animals  are  built  up  of  compounds 
of  the  following  elements  and  these,  therefore,  become  of  the. 
first  importance  to  the  farmer: 

Oxygen  O  Phosphorus     P  Sodium  Na 

Hydrogen  H  Calcium         Ca  Chlorine  Cl 

Carbon  C  Magnesium  Mg  Silicon  Si 

Nitrogen  N  Potassium       K  Flourine  F 

Sulphur  S  Iron                Fe 

A  short  account  of  these  elements  will  be  given  at  this  place. 
Oxygen  (0)  is  the  most  abundant  and  most  important  of  the 
elements.     It  forms  about  half  the  weight  of  the  solid  crust  of 


8 


Agricultural  Chemistry 


the  earth,  eight-ninths  of  the  water,  and  about  one-fifth  of  the 
weight  of  the  air.  In  the  first  and  second  instances  the  oxygen 
is  in  a  combined  state.  That  which  is  held  in  chemical  combina- 
tion in  the  soil  takes  no  part  in  the  formation  of  plant  tissue. 
In  the  atmosphere  it  exists  as  a  free  element,  merely  mixed  with 
the  other  constituents.  Oxygen  in  the  interstices  of  the  soil  is 
an  active  agent  in  bringing  about  many  chemical  changes,  as 
oxidation  of  the  organic  matter  and  disintegration  of  the  soil 
particles.  It  also  forms  about  fifty  per  cent  of  the  compounds 
found  in  plants  and  animals. 

Oxygen  is  a  colorless,  odorless  gas  and  very  slightly  soluble  in 
water.  It  shows  great  tendency  to  combine  with  other  substances 
and  the  act  of  union  is  usually  attended  by  the  production  of 
much  heat.  Burning  or  combustion  is  nearly  always  due  to  the 
heat  produced  by  the  combination  of  the  substance  burned  with 
the  oxygen  of  the  air.  Any  substance,  which  will  burn  in  air 
(containing  about  twenty-one  per  cent  of  free  oxygen)  will  burn 
with  increased  brilliancy  in  pure  oxygen. 

It  is  possible,  with  suitable  apparatus,  to  measure  the  quantity 
of  heat  a  substance  will  produce  when  burned.  The  unit  of  heat 
here  employed  is  the  "calorie,"  which  represents  the  quantity 
of  heat  required  to  raise  one  gram  (about  1-28  of  an  ounce)  of 
water  from  0°  to  1°  on  the  scale  of  the  centigrade  thermometer. 
A  large  Calorie,  one  thousand  times  larger  than  the  above,  is 
employed  for  the  expression  of  large  quantities  of  heat  and  will 
be  employed  here. 

When  one  gram  of  the  following  dry  substances  is  burned  in 
oxygen,  the  quantity  of  heat  produced,  expressed  in  large  Cal- 
ories, is  as  follows : 


Charcoal  8.0 

Hydrogen  34.4 

Wood 2.8 

Coal 7.5 

Coke  7.0 

Casein   .  5.8 


Fat  of  sheep 9.4 

Fat  of  butter 9.2 

Cane  sugar   4.0 

Cellulose 4.1 

Starch  .  4.1 


Introduction  9 

In  ordinary  cases  of  burning,  the  evolution  of  heat  is  readily 
evident,  but  in  some  cases  the  combustion  is  so  slow  that  the 
heat  evolved  is  carried  away  as  fast  as  produced  and  very  slight 
or  no  elevation  of  temperature  is  apparent.  In  some  cases  of 
slow  combustion  where  the  escape  of  heat  is  hindered  from  any 
cause,  the  temperature  may  rise  so  as  to  be  perceptible  or  even 
dangerous.  It  may,  under  particularly  favorable  conditions,  rise 
sufficiently  to  start  a  rapid  combustion  with  oxygen  and  flames 
then  result.  Such  cases  of  "spontaneous  combustion"  frequently 
occur.  Drying  oils,  as  linseed  or  cotton-seed  oil,  especially  when 
spread  on  cotton  waste,  and  fermentation  changes  in  vegetable 
matter  as  hay  and  tobacco  are  notable  examples  of  these  condi- 
tions. 

Hydrogen  (H).  This  element  is  rarely  found  in  a  free  state 
in  nature,  but  is  combined  with  carbon  and  oxygen  as  in  animal 
and  vegetable  matter,  with  oxygen  to  form  water,  and  in  a  few 
cases  with  some  of  the  base  elements  to  form  hydroxides.  It  is 
not  found  in  large  amounts  in  the  soil  and  that  which  forms  a 
part  of  the  tissues  of  plants  and  animals  comes  largely  from  the 
hydrogen  in  water.  It  is  a  colorless,  odorless  gas  and  charac- 
terized by  its  lightness.  This  fact  has  led  to  its  use  for  filling 
balloons,  although  coal  gas  is  now  more  generally  employed  but 
is  not  nearly  so  efficient.  In  a  free  state  it  has  been  found  in 
the  gases  escaping  from  volcanoes. 

Carbon  (C)  is  the  element  most  closely  associated  with  plant 
and  animal  life.  It  forms  a  large  proportion  of  the  solid  matter 
of  all  living  beings;  and  the  chemical  processes  of -animal  and 
plant  life  are  mainly  those  in  which  carbon  plays  an  important 
part.  It  exists  in  the  combined  state  in  many  minerals  as  the 
carbonates  of  calcium,  magnesium,  iron,  zinc,  and  also  in  a  small 
but  very  important  constituent  of  the  air,  carbon  dioxide.  The 
carbon  of  the  soil,  where  it  exists  as  the  main  constituent  of 
organic  bodies,  takes  no  direct  part  in  forming  the  carbon  com- 
pounds of  the  plant.  It  is  not  necessary  to  apply  carbon  fer- 
tilizers to  produce  the  carbon  compounds  of  the  plant,  because 


10  Agricultural  Chemistry 

the  carbon  dioxide  of  the  air  is  the  source  for  crop  production. 
It  is  estimated  that  there  are  about  eighteen  tons  of  carbon  diox- 
ide in  the  air  over  every  acre  of  the  earth's  surface. 

This  element  occurs  in  three  distinct  forms:  (1)  as  the  dia- 
mond, (2)  as  graphite  and  (3)  as  charcoal,  lamp  black,  etc.  The 
diamond  is  crystalline  and  transparent;  graphite  is  crystalline 
but  opaque;  while  lamp  black  and  charcoal  are  non-crystalline. 
The  black  carbon  which  is  produced  when  animal  or  vegetable 
substances  are  strongly  heated  without  access  of  air  (charring) 
is  due  to  the  separation  of  free  carbon  from  the  various  carbon- 
aceous compounds  present. 

Nitrogen  (N)  is  much  less  abundant  in  nature  than  the  ele- 
ments already  described.  A  peculiarity  of  its  occurrence  is  that 
it  appears  to  be  present  only  in  the  outermost  portion  of  the  earth, 
the  greater  portion  being  free  in  the  air.  No  true  minerals  con- 
taining it  are  known  except  those  which  owe  their  origin  directly 
to  plant  or  animal  life,  as  coal,  and  Chili  salt-petre.  All  living 
matter,  however,  contains  it  as  an  essential  constituent.  In  its 
free  state  it  is  a  colorless,  odorless  gas,  showing  little  tendency  to 
combine  with  other  elements.  It  constitutes  about  seventy-nine 
per  cent  of  the  atmosphere  and  over  each  acre  of  land  there  is 
consequently  about  thirty  thousand  tons. 

Although  in  the  free  state  it  is  so  inert,  the  nitrogen  com- 
pounds, as  a  rule,  possess  great  chemical  activity  and  many  are 
very  important  substances.  Some  powerful  drugs  and  poisons 
as  quinine,  strychnine,  and  prussic  acid  contain  nitrogen,  while 
most  explosives,  as  nitro-glycerine  and  gun  cotton  are  also  nitro- 
gen compounds.  It  is  an  absolutely  essential  ingredient  in  the 
food  of  both  animals  and  plants.  It  must  be  supplied  to  animals 
in  compounds  in  which  it  is  combined  with  carbon,  hydrogen, 
oxygen,  and  certain  other  elements  and  which  are  known  as  pro- 
teins, while  plants  acquire  it  generally  from  nitrates,  which  are 
simple  compounds  of  oxygen,  nitrogen,  and  some  base,  as  calcium, 
sodium,  and  potassium.  Only  under  very  special  conditions  can 
some  species  of  plants  obtain  their  necessary  nitrogen  from  the 


Introduction  11 

air.  It  will  be  seen  in  the  later  chapters  that,  although  plants 
are  surrounded  by  air,  rich  in  free  nitrogen,  combined  nitrogen 
is  one  of  the  essential  and  most  valuable  constituents  of  manures. 
A  large  part  of  the  nitrogen  in  the  food  consumed  by  man  and 
animals  is  eliminated  as  simple  compounds  in  the  excreta  and  un- 
fortunately, especially  in  our  cities,  sent  down  the  sewers  and 
rivers  and  finally  discharged  into  the  sea.  To  agriculture  this, 
valuable  combined  nitrogen  is  therefore  wasted.  This  element  is 
the  most  expensive  of  those  necessary  for  plant  growth  and  is 
among  those  liable  to  be  most  deficient  in  our  soils.  No  other  ele- 
ment takes  such  an  important  part  in  agriculture  or  in  life  pro- 
cesses. 

Sulphur  (S)  is  found  both  free  and  combined  in  nature.  The- 
free  element  is  found  in  volcanic  districts,  while  in  the  combined 
state  it  occurs  as  hydrogen  sulphide  in  mineral  waters  and  as  sul- 
phides of  many  metals,  as  for  example  iron,  lead,  and  zinc.  The- 
sulphide  of  iron,  known  as  iron  pyrites,  FeS2,  is  often  mistaken 
for  gold  because  of  its  yellow  color;  sulphur  also  occurs  as  sul- 
phate of  calcium,  in  which  form  it  is  very  widely  distributed  in. 
soils,  and  is  the  main  source  of  the  sulphur  for  crops. 

The  element  sulphur  (brimstone)  is  a  yellow,  brittle  substance 
and  very  inflammable.  It  burns  in  air  with  a  pale  blue  flame,, 
forming  the  suffocating  gas,  sulphur  dioxide.  Such  forms  of  sul- 
phur are  very  poisonous  to  plants  and  animals,  while  sulphates 
are  not  only  harmless,  but  necessary.  Sulphur  is  present  in  the 
proteins  of  both  plants  and  animals  and  when  putrefaction  of 
these  substances  occurs  is  often  liberated  as  hydrogen  sulphide. 
This  substance  is  perceptible  by  its  disagreeable  odor  as  one  of 
the  chief  products  of  the  decay  of  eggs. 

There  is  generally  less  than  0.10  per  cent  of  sulphur  trioxide,. 
as  sulphates  in  ordinary  soil,  and  it  is  now  known  that  the  amount 
required  by  crops  is  considerable ;  for  this  reason  is  may  be  neces- 
sary to  use  certain  sulphates  systematically  as  fertilizers  and  as. 
sources  of  sulphur  for  particular  crops. 


12  Agricultural  Chemistry 

Phosphorus  (P)  always  occurs  in  a  state  of  combination. 
Phosphorus  compounds,  chiefly  phosphates,  are  very  widely  dis- 
tributed, but  in  small  proportion,  in  the  rocks  of  the  earth.  De- 
posits of  calcium  phosphate  'occur  in  certain  localities  and  are 
one  of  the  chief  sources  of  our  phosphate  fertilizers.  All  fertile 
soils  contain  small  quantities  of  phosphates,  which  are  taken  up 
by  plants  and  through  plants  find  their  way  into  animals,  where 
they  accumulate  in  the  bones  or  other  hard  parts,  as  teeth  and 
shells. 

The  element  phosphorus,  as  usually  prepared,  is  a  yellowish 
waxy  substance,  which  has  the  power  of  emitting  a  faint  light 
when  exposed  to  the  air.  This  property  was  the  origin  of  its 
name,  which  is  derived  from  the  Greek  and  means  "the  light 
bearer."  The  emission  of  light  is  due  to  slow  combination  with 
the  oxygen  of  the  air,  resulting  in  the  production  of  heat. 

Phosphorus  is  a  violent  poison.  It  is  largely  used  in  the  man- 
ufacture of  lucifer  matches  and  rat-poison.  For  the  farmer  its 
chief  importance  lies  in  the  use  of  its  compounds,  the  phosphates, 
as  fertilizers,  and  its  occurrence  in  certain  fats  and  protein  com- 
pounds of  feeding  stuffs  and  in  the  bodies  of  animals. 

Soils  are  quite  liable  to  be  deficient  in  phosphates,  as  the  latter 
are  largely  drawn  upon  by  many  crops,  particularly  grain  crops, 
where  the  phosphorus  accumulates  in  the  seed  and  is  sold  from 
the  farm. 

Calcium  (Ca)  is  very  abundant  in  nature,  always  occurring  in 
a  combined  state.  Calcium  carbonate,  CaC03,  is  found  in  enor- 
mous quantities,  as  chalk,  limestone  and  marble,  and  contains  the 
three  elements,  calcium,  carbon  and  oxygen.  It  also  occurs  as 
gypsum,  a  compound  of  calcium,  sulphur  and  oxygen.  The  ele- 
ment itself  is  an  easily  oxidisable  metal,  difficult  to  prepare,  and 
of  no  importance  to  the  farmer.  Its  oxide,  or  a  compound  of 
calcium  and  oxygen,  is  the  important  substance,  quick  lime.  This 
is  made  by  burning  limestone,  whereby  the  carbon  and  part  of 
the  oxygen  are  removed  as  a  gas.  Calcium  is  an  essential  con- 
stituent of  plant  food  and  in  the  soil  is  present  in  a  variety  of 


Introduction  13 

forms,  as  calcium  carbonate,  calcium  sulphate  and  calcium  phos- 
phate. 

Potassium  (K)  occurs  in  many  minerals.  It  will  be  found  in 
many  silicates,  as  orthoclase  or  mica,  which  are  complex  com- 
pounds of  potassium,  silicon,  aluminum,  oxygen  and  other  ele- 
ments. It  also  occurs  in  sea  water,  from  which  sea  weeds  accu- 
mulate large  quantities  of  potassium  compounds.  The  immense 
salt  deposits  at  Stassfurt,  Germany,  furnish  a  large  proportion 
of  the  potassium  used  in  our  potash  fertilizers. 

The  element  is  a  lustrous  metal,  very  soft,  and  so  susceptible 
to  oxidation  that  it  must  be  kept  away  from  contact  with  air  or 
moisture  by  immersion  in  naptha.  By  contact  with  water  it  re- 
acts violently,  producing  much  heat  and  floating  on  the  surface 
of  the  water  with  a  hissing  sound. 

Potassium  compounds  are  of  the  greatest  importance  in  agri- 
culture and  are  necessary  constituents  of  all  fertile  soils.  They 
are  intimately  associated  with  the  growth  and  increase  of  plants 
and  are  always  found  in  greatest  abundance  in  the  twigs,  young 
leaves  and  other  rapidly  growing  portions.  In  some  plants  the 
potassium  is  in  combination  with  certain  organic  acids,  as  citric 
and  tartaric  acids.  In  the  ash  of  plants — that  which  is  left  af- 
ter burning — it  generally  occurs  as  a  carbonate.  Potassium  salts 
are  very  soluble  in  water,  but  are  absorbed  and  retained  by  cer- 
tain constituents  of  the  soil,  so  that  their  loss  by  drainage  from 
soil  is  little  to  be  feared. 

Sodium  (Na)  is  very  widely  distributed  in  nature  and  is  a  con- 
stituent of  many  silicates.  In  the  form  of  sodium  chloride — a 
compound  of  sodium  and  chlorine — it  is  very  plentiful  as  rock 
salt  and  as  the  largest  saline  constituent  of  sea-water. 

Its  properties  resemble  those  of  potassium.  Sodium  compounds 
are  largely  used  in  the  arts  and  the  preparation  of  sodium  car- 
bonate is  one  of  the  largest  and  most  important  of  chemical  in- 
dustries. 

Sodium  is  found  in  the  ash  of  most  plants,  but,  except  in  the 
case  of  certain  plants,  does  not  appear  to  be  essential  to  their 


14  Agricultural  Chemistry 

development.  A  striking  difference  between  sodium  and  potas- 
sium compounds,  which  are  so  much  alike  in  most  of  their  prop- 
erties, is  in  their  behavior  towards  the  soil  when  applied  in  solu- 
tion. The  potassium  salts  are  retained  by  the  clay  and  organic 
matter  in  an  insoluble  form,  but  the  sodium  salts  are  more  easily 
washed  out  by  water  and  escape  into  the  drains.  Although  like 
potassium  in  its  chemical  properties  it  cannot  take  its  place  in 
agriculture. 

Magnesium  (Mg)  is  widely  met  in  nature  as  carbonate  and 
silicate.  The  element  itself  is  a  bright,  silvery  metal,  and  capable 
of  burning  in  air  with  an  intense  and  dazzling  white  light.  Mag- 
nesium is  found  in  the  ash  of  plants  and  is  required  by  all  crops. 
It  is  particularly  abundant  in  the  seeds.  There  is  generally  in 
all  soils  an  amount  sufficient  for  crop  purposes  and  it  is  not  neces- 
sary to  consider  this  element  in  connection  with  fertilizers. 

Iron  (Fe)  occurs  in  a  large  number  of  compounds.  Haematite, 
Fe203,  a  compound  of  iron  and  oxygen,  magnetite,  Fe304,  a  simi- 
lar compound,  but  with  a  different  proportion  of  oxygen,  and 
spathic  iron  ore,  FeC03,  a  compound  of  iron,  carbon,  and  oxygen ; 
the  above  are  all  abundant  minerals  and  valued  as  ores  of  iron. 
The  element  occurs  in  two  states  of  combination  with  oxygen,  one 
a  relatively  small  amount  and  called  ferrous  iron,  the  other  a  rel- 
atively larger  amount  and  designated  ferric  iron.  The  former 
yields  salts  which  are  white  or  green  in  color,  while  those  of  the 
latter  are  red  or  yellow.  Ferrous  compounds  are  often  present  in 
rocks  or  minerals  deep  under  ground,  but  when  brought  to  the 
surface  they  combine  with  the  oxygen  of  the  air  to  form  ferric 
compounds.  The  change  of  the  state  of  iron  is  indicated  by  a 
change  in  color,  often  from  green  or  gray  to  red  or  yellow.  Only 
ferric  compounds  should  exist  in  good  soils.  Iron  is  essential  to 
plants,  but  a  small  quantity  is  all  that  is  required  and  most  soils 
contain  from  one  to  four  per  cent,  an  abundant  supply. 

Chlorine  (Cl)  is  very  abundant,  especially  in  combination  with 
sodium,  as  rock  salt  in  the  sea  and  in  spring  water.  Other  com- 
pounds of  chlorine  also  occur  as  minerals.  The  element  chlorine 


Introduction  15 

is  a  yellowish  green  gas  with  an  irritating  and  suffocating  smell, 
very  soluble  in  water  and  of  great  chemical  activity.  The  prop- 
erties of  chlorine,  which  are  most  valued  in  the  arts,  are  its  bleach- 
ing, disinfecting  and  deodorizing  powers.  It  readily  destroys 
most  coloring  matters  and  is  largely  employed  in  bleaching  vege- 
table textile  fabrics,  as  cotton  or  linen.  It  cannot  be  used  for 
woolen  or  silk  fabrics,  as  it  injures  the  fibres  themselves.  Chlor- 
ine only  bleaches  in  the  presence  of  water  and  it  really  acts  by 
decomposing  the  water,  with  formation  of  oxygen,  which  is  the 
active  agent.  Its  action  as  a  disinfectant  is  probably  due  to  the 
same  process,  the  oxygen  of  the  water  combining  with  the  organic 
matter  and  micro-organisms  and  destroying  them. 

Chlorine  is  present  in  all  soils,  generally  in  combination  with 
sodium,  as  sodium  chloride.  It  is  present  in  all  plants,  although 
its  necessity  for  plant  growth  may  be  questioned.  Crops  have 
been  brought  to  maturity  in  its  entire  absence.  Chlorine  with 
sodium,  as  common  salt,  is  sometimes  used  as  an  indirect  fertilizer. 

Silicon  (Si)  is  extremely  abundant  in  the  rocks  of  the  earth's 
crust,  and  though  it  forms  a  very  important  ingredient  in  soils 
and  occurs  in  most  plant  ashes,  it  does  not  appear  to  be  abso- 
lutely essential  as  a  plant  food.  Some  recent  work,  however,  has 
shown  that  soluble  silica  in  a  soil  enables  a  plant  to  subsist  in  the 
presence  of  a  smaller  quantity  of  phosphoric  acid  than  would  be 
necessary  without  the  silica. 

The  element  itself  is  a  brown  solid  and  at  one  time  was  difficult 
to  prepare  in  any  quantity.  At  present,  with  the  electric  furnace, 
it  is  easily  produced  and  its  price  per  pound  has  been  greatly  re- 
duced. 

The  oxide,  called  silica,  Si02,  is  a  compound  of  silicon  and  oxy- 
gen and  is  a  very  abundant  substance,  occurring  free  as  quartz, 
flint  and  sand;  in  combination  with  metals  the  very  numerous 
and  important  substances  called  silicates,  are  produced.  It  has 
been  estimated  that  nearly  half  of  the  solid  mass  of  the  earth's 
crust  consists  of  silica. 


16  Agricultural  Chemistry 

DEFINITIONS. 

It  now  becomes  necessary  to  define,  in  a  fragmentary  way,, 
some  of  the  commoner  terms  used  in  chemistry. 

Acid.  A  substance  generally  possessing  a  sour  taste  and  the 
property  of  changing  vegetable  blues,  as  blue  litmus,  to  red.  As 
types  of  acids,  we  have  sulphuric  acid,  commonly  used  for  the 
Babcock  test,  and  acetic  acid,  the  principal  acid  in  vinegar.  The 
possession  of  a  sour  taste  and  the  power  of  changing  vegetable 
blues  to  red  is  indicated  by  saying  that  the  substance  has  an  acid 
reaction.  In  a  strictly  chemical  sense  an  acid  is  a  compound  con- 
taining hydrogen  which  may  be  replaced  by  a  metal,  the  product 
formed  being  a  salt.  Thus  in  sulphuric  acid,  H2S04,  the  two 
hydrogen  atoms  may  be  displaced  by  two  atoms  of  sodium,  form- 
ing the  salt  Na2SO4. 

Alkali.  A  substance  opposed  in  its  properties  to  an  acid,  cap- 
able of  neutralizing  and  destroying  the  characteristics  of  an  acid, 
forming  in  so  doing,  a  salt.  The  most  important  alkalies  are 
soda,  potash,  lime,  and  ammonia.  A  substance  is  said  to  have  an 
alkaline  reaction  if  it  turns  certain  vegetable  colors,  as  red  litmus 
to  a  blue  color.  As  a  sample  of  an  alkali  or  base  we  have  potas- 
sium hydroxide,  KOH,  which  is  an  hydroxide  of  a  metal.  This 
can  react  with  an  acid  forming  a  salt  or  neutral  body  as  follows : 

2KOH+H2SO4=K2S04+2H20 

Organic  matter,  strictly  speaking,  is  matter  which  has  been 
produced  by  organisms,  such  as  plants  or  animals,  but  the  term 
is  used  in  a  wider  sense  in  chemistry  for  any  compound  of  car- 
bon whether  produced  by  life  processes  or  artifically.  Almost  all 
forms  of  organic  matter,  when  strongly  heated  out  of  contact 
with  air,  blacken,  owing  to  the  liberation  of  carbon.  With  free 
access  of  air,  combustion  occurs,  and  carbon  dioxide  and  other 
products  are  formed. 

Oxidation  and  reduction.  By  oxidation,  literally  speaking, 
is  meant  union  with  oxygen,  but  in  a  chemical  sense  the  term  is 


Introduction  17 

given  a  wider  significance,  that  is,  combination  with  more  oxygen 
or  with  some  substance  playing  the  part  of  oxygen. 

Reduction  is  used  in  exactly  the  opposite  sense.  A  substance 
which  brings  about  oxidation,  is  called  an  "oxidizing  agent" 
while  one  which  removes  oxygen  is  called  a  "reducing  agent." 
Common  oxidizing  agents  are  air,  nitric  acid,  nitrates  and  chlor- 
ine ;  common  reducing  agents  are  easily  oxidizable  metals,  as  zinc, 
and  many  forms  of  decaying  organic  matter. 

Fermentation.  A  process  of  decomposition,  often  accompan- 
ied by  the  oxidation  of  carbonaceous  matter,  and  produced  by 
the  life  processes  of  bacteria,  yeasts  and  molds.  When  the  process 
occurs  out  of  free  access  of  air  and  bad  smelling  gases  are 
formed,  the  process  is  called  putrefaction. 

The  constituents  of  plants.  All  agriculture  depends  upon  the 
growth  of  plants  and  consequently  all  profit  for  the  farmer  de- 
pends upon  the  value  of  the  crop  his  farm  produces.  This  is 
true  whether  the  crop  is  sold  directly  from  the  farm  or  whether 
it  is  fed  to  animals  and  the  products  such  as  live  stock,  beef,  pork, 
wool,  eggs,  or  milk,  used  as  the  source  of  revenue.  If  the  crops 
now  produced  on  two  hundred  acres  of  land  could  be  grown  on 
one  hundred  without  a  great  increase  of  labor  and  other  expense, 
the  profit  would  be  greater.  Successful  farmers  have  demon- 
strated that  the  present  average  of  crops  can  be  doubled,  and  that 
at  a  cost  per  acre  scarcely  more  than  is  now  required  for  the  one- 
half  crop. 

To  accomplish  this  requires  a  broader  knowledge  of  the  food 
requirements  of  plants  than  is  possessed  by  most  of  our  farmers. 
A  thorough  understanding  of  the  subject  of  plant  food  and  plant 
nutrition  by  our  forerunners  in  agriculture  would  have  rendered 
it  unnecessary  to  emphasize  constantly  the  relation  of  the  con- 
stituents of  the  plant  to  soil  exhaustion. 

It  is  common  experience  that  continued  cropping  results  in  a 
loss  of  fertility.  The  productiveness  of  a  virgin  soil  seems  un- 
limited, for  large  crops  are  produced  from  year  to  year  with  no 


18  Agricultural  Chemistry 

apparent  decrease.  But  sooner  or  later  they  begin  to  diminish 
in  size,  gradually  to  be  sure,  but  unceasingly,  until  at  last  the 
yield  becomes  so  small  as  to  make  the  cost  and  labor  of  production 
unprofitable. 

At  the  Experiment  Station  at  Rothamsted,  England,  barley 
grown  continuously  on  the  same  plot  for  forty-three  years  with- 
out the  use  of  fertilizers  of  any  kind,  yielded  in  the  forty-third 
year  10  bushels  of  dressed  grain  per  acre,  the  average  for  the 
last  eight  years  being  11%  bushels.  Wheat  grown  for  fifty  years 
in  the  same  way  produced  in  the  fiftieth  year  9%  bushels  of  grain 
per  acre,  the  average  for  the  last  eight  years  being  111/2  bushels. 
The  soil  seems  capable  of  keeping  up  the  yield  indefinitely,  but 
the  amount  of  crop  produced  ceases  to  be  profitable. 

It  is  evident  that  the  virgin  soil  must  have  contained  large 
amounts  of  some  substances  that  were  necessary  for  vigorous 
plant  growth  and  that  these  were  removed  by  the  successive  crops 
when  harvested.  The  rapid  decrease  in  fertility  finds  its  most 
rational  explanation  on  this  basis.  Changes  in  climate  and  phy- 
sical condition  of  the  soil  are  inadequate  as  explanations  for  this 
decreased  productive  power. 

A  description  of  the  elements  important  to  agriculture  has  al- 
ready been  given  and  the  very  reason  for  their  importance  to  the 
farmer  lies  in  the  fact  that  they  are  the  elements  which  constitute 
the  compounds  of  plants  and  are  removed  from  the  soil  when  the 
crop  is  harvested. 

Source  of  elements.  However,  not  all.  of  the  elements  de- 
scribed have  come  from  the  soil.  Plants  obtain  the  elements  of 
which  they  are  built  up  partly  from  the  soil  and  partly  from  the 
atmosphere.  From  the  soil  they  obtain  by  means  of  their  roots 
all  their  ash  constituents,  all  their  sulphur  and  phosphorus,  and 
in  most  cases,  nearly  the  whole  of  their  nitrogen  and  water. 
From  the  atmosphere  they  obtain,  through  the  instrumentality  of 
their  leaves,  the  whole  or  nearly  the  whole,  of  their  carbon. 
There  are  exceptions,  especially  in  regard  to  nitrogen,  which  is 
obtained  from  the  atmosphere  by  certain  plants,  such  as  alfalfa, 


Introduction  19 

clover,  vetch,  pea  and  bean,  under  certain  conditions  to  be 
described  later. 

Composition  of  the  plant.  The  most  abundant  ingredient  of 
a  living  plant  is  water.  Many  succulent  vegetables,  as  the  turnip 
and  lettuce  contain  more  than  ninety  per  cent  of  water.  The 
green  corn  plant  contains  eighty-five  to  ninety  per  cent  of  water. 

Combustible  part  of  plants.  If  a  stalk  of  corn  is  dried  and 
burned  the  greater  part  is  consumed  and  passes  away  in  the 
form  of  gas.  But  there  is  always  left  behind  a  small  quantity  of 
white  ash,  corresponding  exactly  to  the  ash  left  in  the  stove  after 
a  stick  of  timber  is  burned. 

The  constituents  which  form  the  dry  matter  of  plants  may  be 
divided  into  two  classes — the  combustible  and  the  non-combusti- 
ble part.  The  combustible  part  of  plants  is  made  up  of  six 
chemical  elements — carbon,  oxygen,  hydrogen,  nitrogen  and  sul- 
phur, with  a  small  amount  of  phosphorus.  Without  these  no 
plant  will  grow.  Carbon  generally  forms  about  one-half  of  the 
dry  combustible  part  of  plants.  Nitrogen  seldom  exceeds  four 
per  cent  of  the  dry  matter  and  is  generally  present  in  much 
smaller  amounts.  Sulphur  and  phosphorus  are  still  smaller  in 
quantity.  The  remainder  is  made  up  of  oxygen  and  hydrogen. 
The  carbon,  hydrogen  and  oxygen  form  the  cellulose,  starch, 
lignin,  gummy  matters,  sugars,  fats  and  vegetable  acids  which 
plants  contain.  The  same  elements  united  with  sulphur  and 
nitrogen  form  the  very  important  proteins,  which  are  the  life 
centers  of  the  plant.  When  all  the  above  elements  are  united 
to  phosphorus,  we  have  additional  important  groups  of  plant 
compounds,  called  nucleins  and  lecithins.  The  lecithins,  how- 
ever, contain  no  sulphur. 

Non-combustible  part  of  plants.  The  non-combustible  or  ash 
constituents  form  generally  but  a  small  part  of  the  plant.  A 
fresh,  mature  corn  plant  will  contain  about  1.2  per  cent  of  ash, 
while  the  corn  grain  when  dry,  contains  about  1.5  per  cent.  In 
the  straw  of  cereals  the  ash  constitutes  4  to  7  per  cent  and  cereal 
grains  2  to  3  per  cent  of  the  dry  matter.  In  hay  5  to  9  per  cent 


20 


Agricultural  Chemistry 


will  be  found.  We  find  in  leaves,  especially  old  leaves,  the  great- 
est proportion  of  ash.  In  the  leaves  of  root  crops  the  ash  will 
amount  to  10  to  25  per  cent  of  the  dry  matter. 


Water  cultures  of  buckwheat.     This  method  of  experimental  culture, 
which  is  known  as  water  culture,  has  been  of  the  greatest  service 
in  determining  which  elements  are  essential  for  plant  growth. 
No.  1.     Plant  grown  in  normal  solution. 
No.  2.     Plant  grown  in  normal  solution  without  potassium. 
No.  3.     Plant  grown  in  normal  solution  with  sodium  instead  of 

potassium. 

No.  4.     Plant  grown  in  normal  solution  without  calcium. 
No.  5.     Plant  grown  in  normal  solution  without  nitrogen. 

Essential  elements.  The  non-combustible  ash  always  contains 
six  elements — potassium,  magnesium.,  calcium,  iron,  phosphorus 
and  sulphur.  It  was  once  thought  that  these  ash  elements  were 
accidental,  simply  dissolved  in  the  soil  water  and  absorbed  by  the 


Introduction  21 

plant  and  that  they  were  not  essential  to  its  development.  Liebig 
proved  that  they  were  necessary;  seeds  were  planted  in  pure 
quartz  sand  contained  in  a  series  of  pots  to  one  of  which  nitrogen 
compounds  alone  were  added,  and  to  the  others,  nitrogen  com- 
pounds plus  a  small  amount  of  plant  ash.  The  plants  in  the  pots 
which  received  the  ash  grew  to  maturity,  while  those  in  the  other 
pots  made  only  a  feeble  growth. 

Non-essential  elements.  Besides  the  elements  just  named  an 
ash  will  generally  contain  sodium,  silicon,  chlorine,  and  fre- 
quently manganese,  and  perhaps  minute  traces  of  other  elements. 
These  elements  just  named  sometimes  form  a  considerable  portion 
of  the  ash.  For  the  reason  that  plants  have  been  brought  to 
maturity  in  their  absence,  it  has  been  generally  accepted  that 
they  are  non-essential.  However,  it  is  necessary  to  remember 
that  such  experiments  have  generally  extended  over  a  single  gen- 
eration and  that  it  is  possible  that  an  attempt  to  grow  the  crop 
through  successive  generations  from  its  own  seed  in  a  soil  devoid 
of  sodium,  chlorine,  silica,  or  manganese  might  meet  with  failure. 

How  ash  elements  occur.  The  ash  elements  named  above  oc- 
cur in  part  in  the  plant  as  salts,  being  combined  with  phosphoric, 
nitric,  sulphuric  and  various  vegetable  acids  of  which  acetic, 
CH3COOH,  oxalic  (COOH)2,  malic,  C2H3OH(COOH)2,  tartaric, 
(CHOHCOOH)2,  and  citric  acids,  C3H4OH(COOH)3,  are  the 
most  common.  It  is  also  very 'certain  that  part  is  in  combination 
with  the  organic  or  combustible  part  of  the  plant.  Sulphur 
occurs  partly  as  sulphates  and  also  as  a  constituent  of  proteins ; 
phosphorus  as  a  phosphate  in  the  stem  and  root  of  the  plant,  but 
in  organic  form  in  its  seeds.  In  addition,  such  ash  elements  as 
potassium,  magnesium,  calcium,  iron  and  silicon  are  very  prob- 
ably in  part  constituents  of  the  organic  compounds  of  plants. 

It  is  usual  to  speak  of  the  combustible  ingredients  of  a  plant 
as  organic,  and  of  the  non-combustible  ingredients  as  inorganic. 
This  is  not  accurate,  as  these  ash  constituents,  which  are  essential 
for  the  growth  of  the  plant,  have  during  its  life  as  much  right  to 
be  called  organic  as  the  carbon  of  starch  or  protein. 


22 


Agricultural  Chemistry 


Can  one  element  displace  another?  The  fact  that  some  of  the 
elements  found  in  plant  ash,  as  sodium  and  potassium,  are  chem- 
ically very  much  alike,  has  led  to  the  attempt  to  displace  the 
expensive  and  less  commonly  occurring  potassium  by  the  inex- 
'pensive  and  relatively  abundant  element,  sodium.  If  it  were 
possible  to  do  this,  the  farmer 's  fertilizer  bills  for  potassium  salts 
would  be  materially  reduced.  However,  experiments  have  dem- 
onstrated that  sodium  cannot  take  the  place  of  potassium  in  the 
growth  of  land  plants. 

A  definite  amount  of  all  the  essential  elements  is  needed  for  a 
certain  yield  and  none  of  the  elements  can  be  replaced  by  an- 
other. A  crop  will  be  limited  by  the  quantity  of  the  essential 
element  present  in  least  quantity  compared  with  the  require- 
ments of  that  crop.  If  a  field  of  corn  can  obtain  only  potash 
enough  for  a  half  crop,  no  more  than  this  can  be  produced,  no 
matter  how  much  of  the  other  forms  of  plant  food  is  present. 

The  following  table  shows  the  ingredients,  expressed  as  pounds, 
in  1000  Ibs.  of  the  matured  corn  plant,  when  the  plant  is  to  be 
cut  for  shocking: 


Corn  Plant 

luooibs. 


Water 

793 


.Hydrogen...    88.1 
I  Oxygen 704.9 


Dry  matter 
207 


Organic  matter 
195 


Ash  12 


!  Protein     18 

Fat 5 

Fiber 50 
Carbohydrates..  122 

Chlorine 0.4 

Potash 4.0 

Phosphoric  acid .  1.2 

Lime s..  1.6 

Magnesia 1.4 

Iron  oxide 0.8 

Sulphur  trioxide     0.8 

Soda 0.4 

Silica    2.4 


f  Nitrogen 
I  Carbon  . 
1  Oxygen  . 
[Hydrogen  ....  12.7 


2.9 
90.5 
88.9 


All  the  elements  mentioned  above  as  occurring  in  the  ash,  with 
the  exception  of  chlorine,  are  combined  with  oxygen.  In  the 
table  the  names  under  "ash"  represent  these  combinations:  pot- 
ash, K2O,  is  composed  of  potassium  and  oxygen ;  phosphoric  acid, 


Introduction  23 

P205,  of  phosphorus  and  oxygen ;  lime,  CaO,  of  calcium  and  oxy- 
gen; sulphur  trioxide,  S03,  of  sulphur  and  oxygen.  The  term 
phosphoric  acid  is  really  the  compound  H3P04,  but  in  agricul- 
tural literature  it  is  common  to  speak  of  the  compound  P205, 
which  chemically  is  phosphorus  pentoxide,  as  phosphoric  acid. 
While  technically  incorrect,  yet  in  this  book  that  nomenclature 
will  be  followed. 

The  table  shows  that  three  elements,  hydrogen,  oxygen  and  car- 
bon, make  up  98^  per  cent  of  the  entire  composition  of  the 
plant,  the  remaining  elements  constituting  only  11^  per  cent. 


CHAPTER  II 
THE  ATMOSPHERE 

The  atmosphere  or  air  forms  an  invisible  envelope  surrounding 
and  resting  upon  the  earth.  It's  exact  thickness  is  unknown,  for 
it  blends  gradually  with  the  imperceptible  ether  which  fills  inter- 
planetary space.  While  its  functions  are  less  apparent  than 
those  of  water  and  soil,  it  nevertheless  bears  important  relations 
to  agricultural  life  and  industries. 

Weight  of  the  air.  The  resistance  which  air  offers  to  rapidly 
moving  bodies,  its  own  motion  as  wind  and  the  support  of  clouds 
and  other  bodies  are  evidences  of  its  mass.  The  pressure  by 
which  it  forces  water  into  the  vacuum  of  a  pump  or  balances  a 
column  of  mercury  in  the  barometer  is  a  measure  of  its  weight, 
which  is  approximately  15  pounds  per  square  inch  at  sea  level, 
or  41,300  tons  for  each  acre  of  the  earth's  surface.  Were  the 
air  of  uniform  density  throughout,  its  height  could  be  easily 
measured.  The  barometer  falls,  however,  with  decreasing  rapid- 
ity as  it  is  raised  from  the  earth,  thus  proving  that  the  air  de- 
creases in  density  with  increase  in  height. 

Height  of  the  air.  The  band  of  haze  attending  the  earth's 
shadow  at  lunar  eclipse,  the  twilight  period  upon  the  earth,  the 
time  of  falling  meteors  and  other  phenomena  dependent  upon 
the  atmosphere  give  means  of  estimating  its  approximate  height 
as  at  least  200  miles. 

Air  essential  to  life.  If  an  animal  be  enclosed  with  a  supply 
of  food  in  a  perfectly  tight  chamber  but  with  a  limited  supply  of 
air  it  will  finally  suffocate.  This  occurs  as  a  result  of  exhausting 
the  greater  part  of  a  constituent  of  the  air  known  as  oxygen. 
This  element  is  absolutely  essential  to  the  processes  by  which  food 
ds  assimilated  and  waste  matter  is  expelled  from  the  animal  body. 


The  Atmosphere  25 

So  too,  if  a  plant  be  similarly  enclosed,  it  will  finally  cease  to 
grow  and  prematurely  die.  This  is  because  it  exhausts  the  lim- 
ited supply  of  carbon  dioxide,  a  constituent  of  the  air,  which 
is  the  basal  material  for  all  compounds  made  by  the  growing 
plant.  The  burning  of  wood  is  a  chemical  process  in  which  oxy- 
gen of  the  air  unites  with  the  chemical  constituents  of  the  wood. 
If  the  fire  be  banked  or  otherwise  deprived  o.f  a  liberal  air  sup- 
ply, it  smoulders.  "When  air  is  liberally  supplied,  as  through  the 
stove  drafts  or  forge  bellows,  combustion — and  the  resultant  heat 
— are  greatly  increased,  as  a  consequence  of  the  increased  supply 
of  oxygen.  The  formation  of  humus  in  the  soil,  the  fermenta- 
tion of  manures,  and  many  other  common  phenomena  of  the 
farm,  are  in  part  processes  of  oxidation  or  burning  on  a  small 
scale,  and  are  dependent  upon  proper  supplies  of  the  oxygen  of 
the  air. 

Atmosphere  controls  rainfall.  The  atmosphere  contains  vary- 
ing amounts  of  water.  Warm  air  has  great  capacity  for  holding 
water  and  may  take  up  large  amounts  from  the  sea  and  inland 
lakes.  Movements  of  this  water-laden  air  control  rainfall.  In 
the  case  of  the  warm,  moisture-laden  winds  moving  eastward 
from  the  Pacific  ocean,  the  water  is  released  when  the  air  is 
cooled  on  the  snow  clad  summits  of  the  mountains  along  the 
Pacific  coast.  In  a  similar  manner  atmospheric  moisture  moving 
westward  is  precipitated  on  the  Rocky  Mountains.  As  a  result 
large  areas  between  these  mountain  ranges  and  to  the  east  of  the 
Rockies  receive  little  or  no  rainfall  and  farmers  are  obliged  to 
practice  dry  farming  or  irrigate  on  arable  land  of  these  regions. 

Atmosphere  controls  temperature.  Dry  air  transmits  heat 
readily  from  the  sun  to  the  earth  or  from  the  earth  into  space. 
For  this  reason  the  temperature  falls  rapidly  after  sunset  in  dry 
winter  weather.  Dry  air  also  permits  rapid  evaporation  of  water 
from  the  earth's  surface  with  consequent  cooling.  Moist  air,  on 
the  other  hand,  prevents  rapid  evaporation  from  the  earth's  sur- 
face, absorbs  heat  transmitted  from  the  sun  and  radiated  from 
the  earth,  and  thereby  maintains  higher  temperatures. 


26 


Agricultural  Chemistry 


While  the  phenomena  of  temperature,  moisture  content,  and 
movement  of  the  air  do  not  directly  involve  chemical  processes, 
they  have  fundamental  significance  in  the  supplying  of  water  and 
the  maintaining  of  temperatures  which  regulate  the.  chemical  pro- 
cesses of  plant  growth.  This  significance  has  been  a  prominent 
factor  in  the  development  of  the  present  extensive  Weather 
Bureau  service  of  the  United  States  government.  The  records 
of  this  Bureau  are  of  great  service  not  only  in  predicting  storms 
and  frosts,  but  in  mapping  restricted  areas,  such  as  the  sugar 
beet  belt,  which  will  be  favorable  for  certain  crops  dependent 
upon  uniform  temperature  and  proper  amounts  of  sunshine  and 
rainfall. 

Air  is  a  mixture.  A  chemical  compound  is  characterized  by 
uniform  composition.  That  is,  the  constituents  of  a  single  com- 
pound occur  in  the  same  proportions  throughout  its  mass.  This 
is  not  true  for  air,  as  the  f ollowing  table  shows : 

Percentage  Composition  of  the  Atmosphere  at  Different  Levels. 


Height  in  feet 

3280 

32,800 

65,600 

164,  000 

328,000 

Nitrogen  

Per  cent 
by  vol. 
78.04 

Per  cent 
by  vol. 
81.05 

Per  cent 
by  vol. 
85.99 

Per  cent 
by  vol. 
89.62 

Per  cent 
by  vol. 
95.35 

Oxygen  

20.99 

18.35 

13.79 

10.31 

4.65 

Argon    

0.94 

0.58 

0.22 

0.07 

0.00 

Carbon  dioxide  

0.03 

0.02 

.004 

0.00 

0.00 

The  air  is  a  mixture  of  water  vapor,  gases,  and  solids  in  which 
the  gases  form  far  the  greatest  part.  Since  it  is  a  mixture,  the 
constituents  are  free  to  separate  and,  as  the  above  table  shows, 
the  heavier  constituents  are  absent  in  the  higher  layers. 

Composition  of  air.  The  average  composition  of  dry  air  is  as 
shown  in  the  table  on  page  27. 

Water  of  the  atmosphere.  The  water  used  by  plants  is  taken 
up  from  the  soil  by  way  of  the  roots.  Its  passage  through  the 
plant  and  the  escape  of  excess  of  water  are  regulated  by  the 


The  Atmosphere 


27 


process  of  transpiration  or  evaporation  from  the  surface  of  the 
leaves  into  the  air.  From  the  current  of  water  thus  maintained 
from  the  soil  to  the  plant,  growing  crops  assimilate  all  of  their 
food  except  carbon  dioxide.  When  the  air  is  dry  it  absorbs  water 
readily  and  promotes  transpiration.  Moist  air,  on  the  contrary, 
retards  transpiration.  By  these  influences  over  transpiration 
the  air  exercises  control  over  plant  growth. 

As  has  been  stated,  the  presence  of  water  in  the  air  increases 
its  capacity  to  absorb  heat  and  when  the  air  is  cooled  it  loses  its 
power  to  retain  moisture.  Water  then  separates  from  it  and  col- 
lects upon  colder  objects.  This  is  the  cause  of  the  appearance  of 
drops  of  water  on  the  outer  surface  of  an  ice-water  pitcher  on 
a  sultry  day  in  summer.  Dew  is  formed  in  the  same  manner. 
After  sunset  on  a  warm  summer's  day  the  earth  cools  rapidly  by 
radiation  and  reaches  a  temperature  below  that  of  the  adja- 

The  Average  Composition  of  Dry  Air. 


Per  cent,  by  weight 
Lbs.  per  100  Ibs. 
of  air. 

Per  cent.  by.  volume 
Gals,  per  iOO  gals. 
of  air. 

Gases:    Nitrogen  

75.5 

78.0 

Oxygen  

23.0 

21.0 

Argon  

1.0 

0.94 

Carbon  dioxide  
Ammonia  

0.04 
Trace 

0.03 
Trace 

Nitric  acid  

i 

it 

Ozone  

< 

{« 

Solids:    Dust  

i 

n 

Bacteria  

< 

n 

Salts  

i 

(i 

cent  air.  At  a  temperature  bearing  a  definite  relation  to  the 
moisture  content  of  the  air  and  known  as  "the  dew  point," 
moisture  leaves  the  air  and  collects  upon  the  surface  of  vegeta- 
tion and  other  cool  objects.  In  rainless  regions  dew  becomes  an 
important  source  of  water  for  crops  and  frequent  tilling  must 


28  Agricultural  Clwmistry 

be  practiced  to  prevent  its  escape  by  evaporation  from  the  sur- 
face of  the  soil. 

Movements  of  the  moisture  laden  air  distribute  rainfall  over 
the  land;  and  some  of  the  less  prominent  constituents  of  the  air 
are  washed  to  the  soil  by  rain  and  become  factors  in  the  supply 
of  plant  food. 

Gases  of  the  air.  Dry,  pure  air  is  essentially  a  mixture  of 
gases.  A  gas  differs  from  the  more  familiar  forms  of  matter,  as 
liquids  and  solids,  in  that  its  particles  are  much  farther  removed 
from  one  another,  or  as  we  say,  it  has  less  density.  This  relation 
is  illustrated  by  the  different  forms  which  water  may  assume. 
When  the  solid  substance  known  as  ice  is  heated,  its  particles 
spread  farther  apart  until  it  no  longer  has  sufficient  cohesive 
power  to  retain  its  shape.  It  then  melts  and  becomes  the  liquid 
known  as  water.  Sufficient  further  heating,  by  separating  the 
particles  of  water  still  farther  apart,  transforms  it  to  the  state 
of  an  invisible  gas  known  as  steam,  which  becomes  a  constituent 
of  the  gaseous  atmosphere.  "When  steam  comes  in  contact  with 
cold  solid  objects,  or  even  with  cold  air,  it  contracts  or  condenses 
to  visible  water  vapor.  The  gases  of  the  air  maintain  their  rari- 
fied  form  under  all  ordinary  conditions.  They  can  be  converted, 
however,  like  the  air  itself,  to  liquids,  and  even  to-  solids,  by 
subjecting  them  simultaneously  to  very  low  temperatures  and 
high  pressures. 

Nitrogen.  This  is  the  most  considerable  constituent  of  the 
air  and  amounts  to  more  than  three-quarters  of  the  total  weight, 
or  about  30,000  tons  over  every  acre  of  land.  It  is  characterized 
by  extreme  inertness.  When  combined  in  chemical  compounds 
it  is  frequently  held  with  difficulty.  High  power  explosives  de- 
pend for  their  value  upon  the  ready  and  sudden  release  of  a 
large  volume  of  gaseous  nitrogen  from  less  bulky  compounds  as 
nitro-cellulose  and  nitro-glycerine.  Since  nitrogen  is  an  essential 
constituent  of  compounds  of  the  greatest  importance  in  the  liv- 
ing cells  of  plants  and  animals,  its  ready  escape  from  such  com- 


The  Atmosphere 


pounds  during  the  decay  of  plant  and  animal  tissues  has  pre- 
sented one  of  the  greatest  problems  of  agriculture. 

Relation  of  nitrogen  to  plant  growth.  The  work  of  several 
able  investigators  has  proved  conclusively  that  higher  plants 
cannot  draw  directly  upon  the  great  stores  of  nitrogen  in  the  air 
for  their  supply  of  this  element. 

In  1855  the  French  chemist  Boussingault  announced  the  re- 
sults of  a  series  of  carefully  performed  experiments  to  deter- 
mine this  point.  He  grew  plants  for  one  and  one-half  to  five 
months  with  no  nitrogen  supply  beyond  that  in  the  seeds  and 
the  free  nitrogen  of  the  air.  The  seed  was  sown  in  a  soil  com- 
posed of  ignited  pumice  stone  and  the  ashes  of  manure,  both 
having  been  freed  from  nitrogen  compounds.  The  plants  were 
grown  in  a  glass  jar  sealed  from  the  air  but  in  connection  with 
a  supply  of  carbon  dioxide  and  were  provided  also  with  water 
free  from  nitrogen.  At  the  end  of  the  experiments  the  nitrogen 
was  determined  in  the  plants  and  soil. 

The  following  table  gives  the  results  of  five  of  the  experiments 
and  the  average  of  the  series: 


Kind  of  Plant. 

Nitrogen  in 
Seeds. 

Nitrogen  in 
Crop  and 
Soil. 

Gain  (-{-)  or 
Loss  (  —  ) 
of  Nitrogen. 

Bean  

gins.* 
0  0349 

gms. 
0  0340 

gms. 
—0  0009 

Oat  

0.0031 

0.0'.  30 

—  0.0001 

Lupin  

0.0200 

0.0204 

-f  0.0004 

Lupin  

0.0399 

0.0397 

—  0.0002 

Cress  

0.0013 

0.0013 

0.0000 

Sum  of  14  Experiments  

0.6135 

0.5868 

—0.0247 

*A  gram  is  about  one-twenty-eighth  of  an  ounce. 

Since  the  gains  or  losses  of  nitrogen  are  within  the  limits  of 
experimental  error,  Boussingault  concluded,  as  a  result  of  his 
work,  that  plants  cannot  use  the  free  nitrogen  of  the  air. 


30  Agricultural  Chemistry 

This  work  was  disputed  by  Ville,  also  of  France,  who  grew 
plants  in  larger  chambers  and  renewed  the  supply  of  air.  He 
criticised  Boussingault 's  work  for  the  limited  amount  of  air 
used.  Boussingault  then  proved  by  further  experiments  that 
plants  raised  under  the  conditions  of  his  earlier  trials  only  at- 
tained full  development  when  supplied  with  assimilable  com- 
pounds of  nitrogen.  An  investigation  of  Ville 's  experiments 
then  showed  that  his  results  were  vitiated  by  the  presence  of 
ammonia  in  his  apparatus. 

The  problem  concerning  the  assimilation  of  free  nitrogen  was 
finally  settled  by  an  exhaustive  study  made  in  1857  to  1858  by 
Lawes,  Gilbert  and  Pugh  at  the  Rothamsted  Experiment  Station 
in  England.  These  investigators  completed  27  experiments  with 
cereals,  legumes  and  buckwheat.  The  plants  were  grown  under 
glass  jars  inverted  in  mercury  to  isolate  them  from  the  air.  A 
supply  of  air,  freed  from  nitrogen  compounds  and  mixed  with 
carbon  dioxide  was  forced  through  the  apparatus  and  all  nitro- 
gen compounds  were  carefully  excluded  from  the  soil  and  water 
used  in  these  experiments.  The  results  fully  confirmed  the  con- 
clusions of  Boussingault. 

In  the  course  of  other  experiments  it  was  observed  that  while 
supplies  of  nitrogen  compounds  in  the  soil  stimulated  the  growth 
of  cereals,  they  were  without  appreciable  effect  upon  legumes. 
It  remained  for  the  German  bacteriologist,  Hellriegel,  to  dem- 
onstrate that  leachings  from  soils  cropped  to  legumes  stimulated 
the  growth  of  these  crops  on  infertile  soils,  but  failed  to  affect 
cereals.  Then  followed  the  discovery  of  a  remarkable  affiliation 
of  bacteria  and  leguminous  plants  by  which  the  plants  obtain 
supplies  of  nitrogen  from  the  atmosphere.  It  has  been  found 
that  certain  bacteria,  existing  in  and  causing  nodules  on  the  roots 
of  these  plants,  derive  food  materials  from  the  plants  and  in  re- 
turn supply  them  compounds  containing  nitrogen,  having  ob- 
tained this  element  from  the  air  in  the  soil.  This  discovery  finds 
a  practical  application  in  the  growth  of  leguminous  crops  in 
rotations  for  the  purpose  of  maintaining  the  supply  of  nitrogen 


The  AtmospJiere 


31 


in  the  soil.  In  field  experiments  the  soil  supply  of  nitrogen  has 
been  maintained  by  growing  clover  in  rotation  ivith  cereal  crops. 
A  small  amount  of  nitrogen  compounds  also  accumulates  in  the 
soil  by  the  growth  of  bacteria  which  thrive  independently  of 
higher  plants. 

Oxygen.  This  constituent  of  the  air  is  prominent  among  the 
chemical  elements  because  of  its  extreme  activity.  It  combines 
with  the  waste  products  from  plant  or  animal  life  in  the  process 
of  combustion  or  decay  and  makes  possible  their  destruction  and 


Clover  obtaining  its  necessary  nitrogen  from  the  air  through  the  action 
of  certain  bacteria.  No.  5  contains  these  bacteria,  while  No.  6 
does  not  (after  Russell  and  Hastings). 

removal.  This  process  is  frequently  accompanied  by  perceptible 
heat,  as  in  the  rapid  combustion  of  fuels,  or  the  less  active  com- 
bustion of  manures  and  silage.  It  is  the  source  of  heat  in  the 
animal  body.  The  hardening  of  so-called  "drying  oils"  is  also 
a  process  of  oxidation.  These  combine  with  the  oxygen  of  the 
air,  in  some  cases  with  sufficient  rapidity  to  produce  a  rise  in 
temperature  causing  spontaneous  combustion.  Destructive  fires 
occasionally  result  from  such  oxidations. 


32  Agricultural  Chemistry 

Oxygen  usually  forms  about  23.2  per  cent  of  the  air  by  weight. 
Where  animal  life  is  abundant  or  where  much  putrefaction  is  in 
progress,  the  percentage  of  it  in  the  air  will  be  reduced.  On 
the  other  hand,  being  exhaled  by  plants,  its  proportion  may  in- 
crease slightly  where  vegetation  is  abundant. 

Argon.  This  gas  forms  most  of  the  remainder  of  the  air.  It 
closely  resembles  nitrogen  in  its  properties.  Argon  is  not  known 
to  be  of  any  importance  to  agriculture. 

Carbon  dioxide,  C02.  Although  usually  forming  a  very 
small  fraction  of  the  air — 0.04  part,  or  less,  by  weight  in  100 
parts  of  air — this  constituent  is  of  great  importance  in  agricul- 
ture. The  average  green  corn  crop  of  12  tons  per  acre  requires 
for  its  production  4  tons  of  carbon  dioxide,  which  necessitates 
the  respiring  of  10,000  tons  of  air,  or  about  one-fourth  the 
amount  available  over  that  acre.  This  supply  of  carbon  dioxide 
is  assimilated  from  air  taken  in  through  the  leaf  pores  or  stomata. 
When  united  with  water  brought  from  the  roots,  it  forms  car- 
bohydrates which  may  be  considered  as  the  basal  compounds  of 
the  plant.  The  removal  of  this  gas  by  plants  is  offset  by  its  re- 
turn from  processes  of  combustion,  fermentation,  and  animal  res- 
piration so  that  there  is  maintained  a  nearly  constant  proportion 
in  the  air.  When  produced  by  the  decay  of  humus- forming  mate- 
rial, it  dissolves  in  the  soil  water  and  becomes  a  leading  factor 
in  liberating  plant  food  from  the  mineral  compounds  of  the  soil. 

Ozone,  03.  This  gas  bears  the  relation  to  oxygen  of  O3 — 
02 — where  02  is  the  molecular  symbol  for  oxygen.  It  is  one-half 
more  concentrated  than  oxygen  and  as  a  consequence  is  much 
more  active.  Ozone  occurs  in  the  air  as  a  result  of  the  action 
of  electrical  discharges  upon  oxygen.  It  acts  as  an  antiseptic  by 
attacking  and  destroying  bacterial  matter.  Because  of  its  great 
activity  as  an  oxidizing  agent,  it  is  rapidly  exhausted  and 
never  amounts  to  more  than  a  trace  in  the  atmosphere. 

Nitric  oxide,  NO.  Traces  of  this  gas  accumulate  in  the 
wake  of  electrical  storms.  It  is  a  compound  of  one  part  of  nitro- 
gen with  one  part  of  oxygen  (14  parts  of  nitrogen  with  16  parts 


The  Atmosphere  33 

of  oxygen  by  weight),  the  formation  of  which  is  induced  by 
electrical  discharges.  Nitric  oxide  readily  unites  with  oxygen 
and  water  to  form  nitric  acid  and  washes  to  the  soil  in  the  rain. 
Knop  found  ordinary  rain  water  at  Leipsig,  Germany,  to  contain 
56  pounds  of  nitric  acid  in  10,000,000  pounds  of  water,  while 
rain  which  fell  during  a  thunder  shower  contained  98  pounds  in 
10,000,000.  Nitric  acid  brought  to  the  earth  in  this  way  is  not 
free  but  combined  with  ammonia  in  the  air.  Reaching  the  soil 
as  ammonium  nitrate  it  is  directly  available  to  the  plant. 

Ammonia,  NH3.  This  gas  accumulates  in  traces  in  the  air 
as  a  result  of  the  decay  of  organic  nitrogenous  compounds.  It 
is  produced  in  considerable  amounts  by  the  rapid  fermentation  of 
manures  and  in  such  cases  may  be  detected  by  its  pungent  odor. 
It  dissolves  readily  in  water  and  washes  to  the  soil  in  rains,  gen- 
erally in  combination  with  nitric  acid.  In  this  form  its  nitrogen 
may  be  used  directly  by  the  plant  or  ultimately  converted  to 
nitrates.  Ammonia  from  this  source  contributes  but  a  small  part 
of  the  nitrogen  required  by  crops. 

The  average  amount  of  nitrogen  brought  to  the  soil  per  acre 
yearly  by  rain  at  the  Rothamsted  Experiment  Station,  over  a 
period  of  18  years  was  as  follows: 

Nitrogen  as  nitrates  and  nitrites   1.1  Ibs. 

Nitrogen  as  ammonia  2.6  Ibs. 

Nitrogen   in   organic    forms    1.0  Ib. 


Total  nitrogen    4.7  Ibs. 

Obviously  this  supply  of  nitrogen  falls  far  short  of  the  50  to 
100  pounds  of  nitrogen  per  acre  required  by  different  crops. 

Solids.  The  solids  usually  present  in  common  air  are  sub- 
stances which  have  been  taken  up  by  the  wind  and  remain  sus- 
pended in  finely  divided  condition.  They  include  bacteria, 
yeast  spores  and  other  microscopic  forms  of  plant  life.  These 
furnish  the  nitrogen  already  referred  to  as  brought  to  the  soil  in 
"organic  forms."  The  air  contains  dust  particles  from  finely 


34  Agricultural  Chemistry 

divided  soil  and  this  constituent  is  prominent  in  dry  regions. 
Spray  from  bodies  of  salt  water,  when  taken  into  the  air  by  wind, 
evaporates  and  leaves  small  quantities  of  salts  suspended.  These 
consist  principally  of  sulphates  and  chlorides  of  sodium,  potas- 
sium, calcium  and  magnesium.  Salts  may  be  returned  to  the  soil 
by  rain  in  considerable  amounts  near  the  sea  coast.  Common 
salt  is  brought  to  the  soil  in  this  manner  at  the  rate  of  186 
pounds  per  acre  yearly  at  Georgetown,  British  Guiana ;  at  Roth- 
amsted,  England,  which  is  farther  inland,  the  amount  is  about 
24  pounds  per  acre.  Sulphur  is  an  important  element  in  the 
growth  of  plants,  and  is  brought  to  the  soil  by  rain  in  the  form  of 
sulphates  taken  up  from  the  sea.  These  supplies  of  plant  food  may 
become  important  factors  in  the  growth  of  corps.  It  has  been 
estimated  that  the  chlorine  in  rain  water  at  Rothamsted  is 
sufficient  for  crops,  with  the  possible  exception  of  mangels,  and 
that  the  sulphur  supplied  in  this  way  meets  the  demands  of  most 
cultivated  crops.  This  high  supply  of  sulphur  may,  however,  be 
derived  partly  from  extensive  soft  coal  burning  in  a  country 
like  England.  It  is  now  known  that  the  sulphur  supply  from 
the  atmosphere  in  the  open  country  of  the  United  States  is  prob- 
ably as  high  as  that  found  at  Rothamsted.  It  is,  however,  prob- 
ably not  nearly  sufficient  for  continuous  crop  requirements. 

Accidental  constituents.  In  some  localities  the  air  contains 
uncommon  constituents  as  a  result  of  local  conditions.  This  is 
true  in  active  volcanic  regions  and  in  the  vicinity  of  some  indus- 
trial plants.  The  most  important  of  these  constituents  are  gases. 
Methane  or  marsh  gas,  which  is  a  product  of  fermentation  where 
air  is  excluded  and  which  accumulates  over  swamps  and  in  mines, 
and  carbon  monoxide,  a  product  from  the  incomplete  combustion 
of  coal,  are  examples  of  this  class.  Hydrochloric  acid  gas,  which 
escaped  into  the  air  in  quantity  from  the  old  process  of  manu- 
facturing soda,  is  an  example  of  an  objectionable,  accidental  con- 
stituent of  the  air  resulting  from  an  industrial  process.  The 
deadly  effect  of  this  gas  upon  vegetation  led  to  the  passage  of 


The  Atmosphere  35 

laws  restricting  its  escape.    It  is  now  condensed  in  the  factory  as 
a  by-product  of  the  industry. 

Sulphur  dioxide  is  an  accidental  gaseous  constituent  of  the 
air,  the  effects  of  which  are  of  economic  importance.  It  is  ex- 
pelled from  the  stacks  of  smelters  roasting  ores  which  contain 


The  effect  of  smelter  fumes  and  waste  on  vegetation  near  Anaconda, 

Montana. 

sulphur.  It  is  also  produced  in  small  amounts  wherever  the 
combustion  of  coal  takes  place.  It  may  be  partially  converted  to 
sulphur  trioxide  and  brought  to  the  soil  by  rain  as  a  supply  of 
sulphur  for  plants.  The  amount  in  the  rain  at  Rothamsted  was 
found  to  be  about  17  pounds  of  sulphur  trioxide  yearly  per  acre. 
Approximately  a  similar  quantity  falls  yearly  in  the  rain  at 
Madison,  Wisconsin. 

Experiments  have  demonstrated  that  sulphur  dioxide  injures 
plants  through  their  leaves.  Fumigation  with  one  part  of  the 
gas  to  100,000  parts  of  air  has  been  fatal  to  scrub  pines.  In- 
vestigations have  shown  it  to  be  the  cause  of  serious  injury  to 


36  Agricultural  Chemistry 

the  vegetation  in  the  vicinity  of  copper  smelters  in  California, 
Montana  and  elsewhere.  The  foliage  of  injured  trees  in  these 
vicinities  was  found  to  contain  more  sulphur  than  that  of  normal 
trees.  Peach  trees  in  an  exposed  position  nine  miles  from  a 
smelter  at  Redding,  California,  and  red  firs  at  a  distance  of 
fifteen  miles  from  the  Washoe  smelter,  Anaconda,  Montana,  were 
badly  injured.  Analysis  of  the  smoke  from  the  latter  smelter 
showed  an  output  of  5,000,000  pounds  of  sulphur  trioxide  per 
day.  Haywood,  of  the  Bureau  of  Chemistry,  concludes  that 
these  fumes  can  be  condensed  and  the  products  probably  readily 
marketed.  Legislation  in  the  interests  of  forestry  should  re- 
strict the  escape  of  this  gas  as  it  has  in  the  case  of  hydrochloric 
acid. 


CHAPTER  III 
THE  SOIL 

Soil  is  the  layer  of  disintegrated  rock,  mixed  with  the  remains 
of  plants,  which  covers  a  large  portion  of  the  land.  It  also  con- 
tains living  organisms  of  various  kinds  and  variable  quantities 
of  water  and  air.  The  depth  of  soils  varies  greatly,  being  usually 
from  six  to  twelve  inches,  and  sometimes  as  great  as  several  feet. 
Beneath  it  is  the  subsoil  which  differs  from  the  upper  layer  in 
containing  less  organic  matter.  The  line  of  demarcation  can 
often  be  distinctly  seen  in  deep  trenches  by  the  difference  in 
color,  the  subsoil  being  generally  of  lighter  color,  and  gradually 
grading  into  the  dark  color  of  the  upper  soil. 

Soils  consist  largely  of  disintegrated  rock  fragments  and  de- 
pend for  their  chemical  nature  mainly  upon  the  character  of  the 
rocks  beneath.  The  rocks  have  been  classified  by  geologists  ac- 
cording to  their  origin  into  three  classes: 

(1)  Igneous  rocks  are  those  which  resulted  from  the  cooling 
of  intensely  heated  matter.     The  granites  represent  this  type. 

(2)  Sedimentary  rocks  are  those  resulting  from  the  settling 
out  of  particles  suspended  in  water.     Limestones  are  examples 
of  this  type. 

(3)  Metamorphic  rocks  are  those  which  have  been  changed  in 
character  since  their  deposition.     The  conversion  of  limestone 
into  marble  by  pressure  and  heat  is  an  illustration  of  this  type. 

These  rocks  must  have  contained  all  of  the  mineral  or  ash  ele- 
ments of  plant  food  as  no  other  source  for  them  is  conceivable. 

Rocks  are  rarely  homogeneous,  that  is,  alike  in  all  parts — but 
are  generally  made  up  of  several  components  mingled  together, 
often  lying  side  by  side  as  separate  crystals.  These  components, 

310566 


38  Agricultural  Chemistry 

which  have  a  more  or  less  definite  composition,  are  called  min- 
erals. Distinctly  separate  minerals  are  more  frequently  to  be 
seen  in  the  igneous  rocks.  A  piece  of  granite  will  readily  show 
that  it  is  made  up  of  several  distinct  minerals. 

Minerals.  The  following  minerals  are  abundant  and  of  the 
greatest  importance  to  agriculture : 

Quartz,  Si02,  is  chemically  a  compound  of  silicon  and  oxygen. 
It  is  estimated  that  it  forms  35  per  cent  of  the  solid  crust  of  the 
earth.  It  is  one  of  the  hardest  and  most  durable  of  substances 
and  is  practically  insoluble  in  water  and  but  little  affected  by 
the  weather.  Sea  sand  and  the  sands  along  the  shores  of  our 
fresh  water  lakes  are  often  almost  wholly  made  up  of  fine  grains 
of  quartz,  worn  smooth  by  continuous  agitation  to  which  they 
have  been  subjected.  Fragments  of  quartz,  consisting  of  crystals 
rounded  and  worn  by  mechanical  rubbing  against  each  other, 
form  the  largest  constituent  of  many  soils.  Such  sand  is  lack- 
ing in  plant  food. 

Feldspars  are  probably  the  most  abundant  of  all  minerals  and 
constitute,  it  is  estimated,  48  per  cent  of  the  earth's  crust.  Chem- 
ically, the  feldspars  contain  silicon,  oxygen  and  aluminum  in 
combination  with  either  sodium,  potassium,  or  calcium,  and  are 
called  by  the  chemist,  silicates. 

The  chief  varieties  of  feldspars  are 

Orthoclase,   KoO.AloOo.6SiO^ potassium  aluminum     silicate 

Albite,  Na  O.A1  O  .6SiO sodium       aluminum     silicate 

2  23  2 

Labradorite    (Na  .Ca)O.Al  0  .3SiOo sodium       aluminum     silicate 

2  232 

calcium 

Orthoclase  or  potash  feldspar  is  the  most  important.  It  is  a  hard 
mineral,  often  colored  pink  or  green,  though  sometimes  white. 
Although  hard,  it  is  easily  attacked  by  water  and  carbon  dioxide, 
the  potassium  being  largely  removed  in  solution  while  the  final 
residue  is  kaolin  or  China  clay.  Orthoclase  furnishes  a  consider- 
able quantity  of  the  potash  found  in  our  soils. 

Mica,  K20.3Al203.4Si02,  is  another  abundant  mineral  and 
characterized  by  its  tendency  to  split  into  thin  elastic  plates.  It  is 


The  Soil  39 

essentially  a  compound  of  aluminum,  potassium,  silicon  and  oxy- 
gen, though  it  usually  contains  iron  and  often  calcium  or  mag- 
nesium. Mica  also  suffers  decomposition  under  the  influence  of 
the  weather,  but  not  so  readily  as  the  feldspars.  It  furnishes 
plant  food  in  the  iron,  potassium  and  calcium  it  contains.  Its 
amount  in  the  earth's  crust  has  been  estimated  at  8  per  cent. 

Silicates  of  magnesia  are  also  very  abundant.  Talc  and 
steatite,  6Mg0.4Si02.H20,  are  representatives  of  this  class  and 
are  compounds  of  magnesium,  silicon  and  oxygen,  designated  by 
the  chemist  "silicates  of  magnesia."  They  also  contain  water. 
When  the  magnesium  is  partly  replaced  by  other  elements,  as 
calcium,  iron  or  manganese,  \ve  have  the  distinct  minerals  known 
as  hornblende  and  augite,  Mg,CaFeSi4012.  All  the  minerals  of 
this  class  are  easily  acted  upon  by  water  and  air  and  often  yield 
brightly  colored  clays  due  to  the  presence  of  iron. 

Calcium  carbonate,  CaC03,  occurs  in  a  great  many  crystalline 
forms,  the  principal  variety  being  called  calcite,  and  in  the  mas- 
sive form  is  known  as  chalk,  limestone  and  marble.  These  are  all 
essentially  made  of  calcium,  carbon  and  oxygen,  but  in  certain 
localities  the  calcium  is  more  or  less  replaced  by  magnesium 
which  then  gives  us  the  mineral  known  as  dolomite,  MgC03. 
CaC03.  This  is  true  of  many  of  the  "limestones"  found  in  "Wis- 
consin. Most  calcium  carbonates  contain  notable  quantities  of 
phosphoric  acid.  Calcium  and  magnesium  carbonates,  though  only 
slightly  soluble  in  pure  water,  are  readily  soluble  in  water  con- 
taining, as  in  the  case  of  nearly  all  forms  of  natural  water,  carbon 
dioxide.  Rocks  containing  these  substances  therefore  are  quickly 
eroded  by  exposure  to  the  atmosphere.  Calcium  carbonate  is  of 
great  importance  in  soils,  both  on  account  of  its  providing  plant 
food  and  because  of  its  relationship  to  many  of  the  processes 
which  go  on  in  soils. 

Clay,  Al203.2Si02.2H20,  in  its  pure  form  is  a  hydrated  silicate 
of  aluminum  and  is  therefore  devoid  of  plant  food.  By  the  term 
hydrated  we  mean  that  the  compound  of  silicon,  aluminum  and 
oxygen  (silicate  of  aluminum)  is  joined  to  a  certain  amount  of 


40  Agricultural  Chemistry 

water.  Ordinary  clay,  however,  contains  iron  and  potassium,  the 
latter  remaining  from  the  feldspar,  from  which  most  clays  have 
been  formed.  It  therefore  supplies  potassium  to  plants.  Its 
physical  properties  are  very  important  and  greatly  influence  soils 
in  which  it  is  abundant. 

Apatite  or  crystallized  phosphate  of  lime,  3Ca3(P04)2.CaCl2 
or  3Ca3(P04)2.CaF2,  is  present  in  small  quantities  in  many  of  the 
older  rocks,  and  is  probably  the  original  source  of  the  phosphoric 
acid  of  soils.  Apatite  also  occurs  massive  in  some  of  the  older 
rock  formations  and  is  mined  as  a  raw  material  for  the  manufac- 
ture of  phosphate, manure  in  Norway,  Canada,  and  particularly 
as  plwsphorite,  Ca3(P04)2,  in  some  of  our  southern  states,  as 
Florida,  the  Carolinas,  Georgia  and  Tennessee. 

Selenite,  CaS04.2H20,  called  gypsum  or  "land  plaster," 
when  occurring  massive,  is  found  in  most  rocks  in  well  developed 
crystals.  Distributed  in  soils  and  dissolved  in  the  soil  water, 
selenite  is  probably  the  chief  source  of  the  sulphur  used  by  plants. 

Iron  pyrites,  FeS2,  occurs  in  small  yellow  cubic  crystals  in 
many  of  the  older  rocks,  and  in  a  finely  divided  condition  forms 
the  coloring  matter  of  our  dark  green  rocks  and  clays.  It  decom- 
poses quite  readily  when  exposed  to  the  air,  becoming  oxidized 
to  a  sulphate. 

Limonite,  2Fe2O3-f-3H20,  a  hydrated  oxide  of  iron,  occurs  in 
lumps  and  particles  in  many  of  the  sedimentary  rocks.  In  a  dif- 
fused state  it  is  the  main  coloring  matter  of  soils,  and  it  is  depos- 
ited from  water  containing  the  bicarbonate  of  iron  upon  exposure 
to  the  air.  The  rusty  deposits  and  stains  left  by  the  dripping  of 
many  service  waters  on  porcelain  or  other  surfaces  consist  of 
limonite. 

Zeolites.  These  bodies,  like  clay,  are  secondary  derivatives  of 
silicates.  They  are  polysilicates  containing  aluminum  and  other 
members  of  the  alkali  and  lime  families  and  always  contain  water 
held  in  chemical  combination.  They  are  believed  to  be  important 
factors  in  soil  fertility  and  especially  concerned  in  the  fixation  of 


The  Soil  41 

soluble  salts.  Stilbite,  Al203.Ca0.6Si025H20,  represents  a  type 
of  these  materials. 

A  brief  description  of  some  of  the  more  important  rocks  will 
now  be  given.  The  igneous  rocks  are  the  oldest  and  it  was  from 
the  debris  of  igneous  rocks  that  sandstones,  shales  and,  indi- 
rectly, limestones  were  formed. 

Sand  stones  and  grits,  consist  of  the  larger  fragments  of  the 
waste  resulting  from  the  breaking  up  of  igneous  rocks,  as  for 
example  granite,  which  in  consequence  of  their  size  and  weight 
have  been  deposited  at  or  near  the  mouths  of  rivers.  Their  main 
ingredient  is  silica,  the  grains  of  sand  consisting  largely  of  quartz 
crystals,  but  in  many  cases  fragments  of  feldspars,  mica  and 
other  minerals  are  present.  These  grains  are  cemented  together 
either  by  calcium  carbonate,  as  in  calcareous  sand-stones,  by  clay, 
as  in  argillaceous  sand-stones,  by  iron  oxide,  as  in  ferruginous 
sand-stones,  or  by  silica,  as  in  siliceous  sand-stones.  Soils  pro- 
duced by  the  decay  of  sand-stones  are  light  and  friable  and  poor 
in  plant  food  unless  there  is  present  potassium-containing  min- 
erals as  feldspar  and  mica. 

Shales  consist  principally  of  the  plastic  hydrated  aluminum 
silicate,  kaolin,  AL>03.2Si02.2H20,  but  may  contain  any  other  ex- 
tremely finely  divided  matter  obtained  by  the  erosion  of  the  orig- 
inal rock.  Particles  of  undecomposed  or  partially  decomposed 
feldspars  are  often  present  and  these  are  of  importance  because 
of  the  potash  they  contain.  Soils  formed  from  shales  are  '  heavy ' ' 
and  clayey,  generally  sufficiently  rich  in  potassium,  but  poor  in 
phosphorus  and  calcium  carbonate  (lime). 

Limestones,  in  which  term  chalk  and  magnesian  limestone  may 
also  be  included,  have  been  formed  largely  by  the  abstraction 
from  water  by  living  organisms,  as  coral  polyps,  shell  fish,  etc., 
of  calcium  and  magnesium  carbonates.  Oyster  shells  are  prin- 
cipally calcium  carbonate.  Limestones  often  contain  small  quan- 
tities of  clay,  iron  oxide,  silica  and  nearly  always  calcium  phos- 
phate in  comparatively  large  quantities.  The  soil  left  on  lime- 
stone or  chalk  consists  mainly  of  these  foreign  substances,  most 


42  Agricultural  Chemistry 

of  the  calcium  carbonate  itself  having  been  dissolved  out  by  the 
combined  action  of  water  and  carbon  dioxide.  It  sometimes  hap- 
pens therefore  that  the  soil  originating  on  limestone  would  be 
benefited  by  an  application  of  limestone. 

Limestone  only  exerts  its  characteristic  and  important  func- 
tions in  a  soil  when  in  a  very  finely  divided  state.  In  the  form 
of  gravel  or  sand  it  is  little  better  than  ordinary  siliceous  sand. 
In  the  finely  divided  .state  it  has  two  very  valuable  functions; 
first,  as  a  source  of  plant  food  by  virtue  of  the  calcium  which  it 
contains,  and  second,  which  is  more  important,  as  a  basic  material 
necessary  for  the  correction  of  an  acid  reaction  in  the  soil  and 
for  the  processes  of  nitrification. 

Sedentary  and  transported  soils.  These  terms  are  conven- 
ient in  distinguishing  between  soils  which  have  been  made  up  of 
the  debris  resulting  from  the  weathering  of  the  particular  rock 
on  which  they  rest  (sedentary  soils)  and  those  which  owe  their 
origin,  not  to  the  rock  below  them,  but  to  materials  brought  from 
a  distance  and  deposited  there  (transported  soils).  The  rich 
alluvial  soil  in  the  lower  reaches  of  river  valleys  consists  largely 
of  material  which  has  been  brought  down  by  the  river  from  the 
higher  parts  of  the  valley  and  since  the  materials  in  many  cases 
have  been  brought  from  various  rock  formations,  the  resulting 
soil  generally  possesses  a  greater  fertility  than  would  be  shown 
by  soil  formed  exclusively  by  the  weathering  of  any  one  kind  of 
rock. 

Glaciers  are  also  the  means  of  transporting  large  quantities  of 
materials  out  of  which  soils  may  be  formed.  Large  tracts  of 
country  are  covered  with  a  thick  deposit  of  clay  and  rock  frag- 
ments, which  have  been  brought  from  a  great  distance  by  glaciers. 
Such  deposits  are  known  as  glacial  drift,  and  often  quite  obscure 
the  actual  rock  beneath.  In  this  case  the  transportation  of  the 
soil  took  place  many  ages  ago.  A  large  part  of  northern  United 
States  is  covered  by  drift,  which  was  pushed  down  from  the  north 
by  the  glaciers  that  once  covered  that  section  and  was  left  behind 


The  Soil 


43 


as  the  ice  melted  away.  Such  soils  are  distinguished  from  all 
others  by  the  presence  of  rounded  boulders  of  various  sizes. 
They  are  usually  fertile,  although  very  variable  in  composition. 
Wind  also  sometimes  acts  as  a  means  of  transporting  sand, 
volcanic  ash,  etc.,  from  a  distance  and  deposits  them  in  a  new 
position,  there  to  form  a  soil  called  loess. 


The  weathering  of  rock  into  sub-soil  and  soil   (after  Hall). 

Formation  of  soil.  In  the  formation  of  a  soil  the  first  step 
is  the  mechanical  breaking  down  of  the  rock  into  small  fragments. 
The  chief  agencies  by  which  this  is  accomplished  are,  first  by 
water,  which  acts  in  several  ways. 

Mechanically,  l>y  liquid  water — The  flow  of  water  over  the  sur- 
face of  a  rock  abrades  it  slightly.  The  action  is  greatly  in- 
creased by  the  rubbing  action  of  pebbles  and  gravel,  urged  on 


44  Agricultural  Chemistry 

by  the  current  over  the  rock.  In  this  way  streams  in  the  rapid 
portions  of  a  course  carry  away  large  quantities  of  sand,  gravel, 
etc.,  and  deposit  them  in  the  lower  and  quieter  portions  of  their 
course  as  alluvial  deposits.  By  glaciers — Glaciers  are  slowly 
moving  masses  of  ice.  In  their  descent,  aided  by  fragments  of 
rock  imbedded  in  them,  they  grind  away  the  rock  over  which 
they  pass  and  the  stream  which  flows  from  the  base  of  a  glacier 
is  always  heavily  charged  with  the  finest  mud,  while  the  lowest 
point  reached  by  a  glacier  is  marked  by  huge  piles  of  rock  frag- 
ments of  all  sizes,  carried  down  on  the  surface  of  the  moving  ice. 
By  alternate  frost  and  thaw — Ice  occupies  a  greater  volume  than 
the  water  from  which  it  is  formed.  The  increase  in  volume  in" 
the  act  of  freezing  amounts  to  about  10  per  cent  and  unless  this 
increase  is  allowed  to  occur  water  cannot  freeze,  however  much 
it  be  cooled.  This  is  a  powerful  agency  in  the  pulverization  of 
rocks.  All  rocks  are  more  or  less  porous  and  absorb  water. 
During  the  warm  part  of  a  wet  winter's  day  the  crevices  of  a 
rock  become  filled  with  water.  If  the  temperature  falls  the 
water  begins  to  freeze,  at  first  on  the  surface  so  that  every  crevice 
becomes  plugged  with  ice.  As  the  liquid  within  continues  to  lose 
heat  it  tends  to  solidify.  This  it  can  only  do  if  it  be  allowed  to 
expand  and  in  order  to  do  this  it  must  widen  or  lengthen  the 
crevice.  When  the  next  thaw  comes,  the  enlarged  crevice  again 
fills  with  water.  The  next  freeze  repeats  the  action  and  so  the 
process  goes  on  until  the  hardest  rock  is  broken  into  fragments. 

Chemically.  Many  minerals  when  exposed  to  the  action  of 
water  are  acted  upon  in  such  a  way  as  to  lead  to  their  disintegra- 
tion. A  portion  is  often  carried  away  in  solution  while  the  re- 
mainder .crumbles  and  is  then  easily  moved  by  rain  or  running 
water.  In  many  rocks  the  cementing  material,  which  holds  the 
grains  together,  is<  dissolved  away  and  the  residual  fragments 
then  readily  crumble. 

A  soil  produced  by  mere  mechanical  pulverization  of  the  rocks 
would  not  furnish  proper  food  for  the  higher  plants.  This  can 
readily  be  imagined  if  one  thinks  how  unsuitable  crushed  granite 


The  Soil  45 

would  be  for  plant  production.  The  essential  elements  locked 
up  in  these  insoluble  soil-forming  materials  must  be  changed  into 
materials  that  the  plant  can  assimilate  and  water  is  an  important 
factor  in  bringing  about  such  chemical  changes.  The  minerals 
forming  our  igneous  rocks  are,  however,  very  slightly  soluble  in 
pure  water;  but  the  water  that  enters  the  ground  has  dissolved 
in  it  small  amounts  of  carbon  dioxide,  derived  from  the  air,  and 
water  containing  this  gas  wall  dissolve  these  minerals  in  appre- 
ciable quantities. 

Another  important  agent  in  soil  formation  is  the  air,  which 
acts  in  several  ways. 

Mechanically.  "Wind  actually  detaches  large  projecting  pieces 
of  rock  in  mountainous  districts  and  sends  them  crashing  down 
onto  the  rocks  below.  In  addition,  by  hurling  sand  and  small 
pebbles  against  the  surface  of  rocks  it  brings  about  the  erosion  of 
the  latter.  In  most  cases  the  effects  of  this  form  of  erosion  are 
masked  and  hidden  by  those  of  other  denuding  agencies. 

Chemically.  In  many  rocks  are  minerals  capable  of  taking  up 
oxygen.  On  exposure  to  air,  oxidation  occurs  and  the  mineral 
swells  up  and  often  crumbles  to  powder,  thus  loosening  the  other 
minerals  in  the  rocks.  This  oxidation  is  in  many  cases  accom- 
panied by  a  change  in  color,  from  green  or  gray  to  yellow  or 
red.  The  carbon  dioxide  of  the  air  also  acts  corrosively  on  car- 
bonates in  the  presence  of  water. 

Animals  are  also  important  agencies  in  soil  formation.  Bur- 
rowing animals,  as  for  example,  rabbits,  moles,  etc.,  admit  air 
into  soil  or  sand  and  thus  favor  the  changes  which  air  produces. 
The  part  played  by  the  humbler  creatures,  earth  worms,  is  prob- 
ably much  more  important.  They  bring  portions  of  the  subsoil 
to  the  surface,  they  draw  dead  leaves  and  other  vegetable  refuse 
into  their  burrows,  and  they  pass  large  quantities  of  the  soil 
through  their  bodies  and  deposit  it  on  the  surface  at  a  rate  which 
has  been  estimated  on  the  average  to  be  about  ten  tons  per  acre 
per  year. 


46  Agricultural  Chemistry 

Ants  in  some  hot  countries,  as  for  example  Africa,  perform 
much  the  same  work  as  earth  worms,  though  perhaps  on  even  a 
larger  scale.  Ingle  says  that  in  many  parts  of  South  Africa,  the 
veld  is  thickly  studded  with  the  hills  of  the  white  ant,  usually 
about  two  feet  high  and  about  two  to  three  feet  in  diameter, 
though  much  larger  ones  are  often  found.  The  ant  hills  are  full 
of  cavities  and  chambers  inhabited  by  the  insects  and  much 
vegetable  matter  is  stored  in  them.  The  material  of  the  ant  hills 
consists  of  the  smaller  parts  of  the  surrounding  soil,  the  par- 
ticles being  cemented  together  and  the  whole  made  practically 
water  tight.  When  the  veld  is  plowed  and  sown,  it  is  always 
noticed  that  where  ant  hills  had  formerly  been  the  crop  is  heavier 
than  elsewhere. 

Plants  act  as  soil  formers  in  several  ways:  Meclwnically — the 
roots  penetrate  the  rocks  or  soils,  rendering  them  porous  and  thus 
admitting  air  and  water.  They  also  exert  a  tremendous  lateral 
force,  breaking  apart  rocks  and  stones  when  once  they  have  ob- 
tained a  foothold  in  a  crevice.  The  roots  penetrate  the  soil  some- 
times to  great  depths,  and  as  they  decay,  after  the  death  of  the 
plant,  they  leave  in  the  soil  little  channels,  which  serve  to  carry 
down  water  laden  with  carbon  dioxide,  as  well  as  the  oxygen 
of  the  air,  which  as  previously  pointed  out  are  important  factors 
in  soil  making  and  the  production  of  available  plant  food. 
Chemically — plants  act  during  life  through  the  corrosive  action 
of  the  carbon  dioxide  excreted  by  the  roots  and  root  hairs  and 
after  death  by  producing  carbon  dioxide  and  various  vegetable 
acids,  which  have  solvent  properties  upon  certain  constituents  of 
soils. 

The  formation  of  a  mass  of  pulverized  rock,  however,  is  not 
all  that  is  necessary  for  producing  a  fertile  soil.  A  fertile  soil 
must  contain  nitrogen.  It  has  been  shown  that  to  grow  crops  the 
soil  must  contain  available  nitrogen,  and  this  must  have  been  de- 
rived originally  from  the  air.  Small  quantities  of  combined 
nitrogen,  as  stated  in  a  previous  chapter,  are  carried  into  the 
ground  by  the  rain  water  and  though  small  in  amount,  are  prob- 


The  Soil 


47 


ably  sufficient  to  enable  plant  growth  to  begin.  Bacteriologists 
believe  that  certain  species  of  bacteria,  which  can  live  on  mineral 
food  alone  and  derive  all  their  nitrogen  supply  from  the  air  were 
the  first  agencies  and  are  still  important  factors  in  accumulating 
the  nitrogen  supply  of  the  soil.  Certain  simple  forms  of  plant 


Diagram  illustrating  the  formation  of  a  soil  on  a  limestone  hill  (after 

Vivian) 

life,  as  lichens  and  mosses,  it  is  believed,  can  also  derive  their  nit- 
rogen from  the  atmosphere.  When,  after  death,  a  plant  becomes 
a  part  of  the  soil,  all  the  plant  food  it  contained  is  returned. 
Food,  once  used  by  plants,  is  readily  made  available  to  succeed- 
ing crops  through  processes  of  decay  and  nitrification.  The  soil 
is  thus  made  richer  and  more  fertile.  In  this  way  growth  gradu- 
ally becomes  more  abundant.  The  plants  upon  decay  give  rise 
to  "humus,"  the  chief  nitrogen  containing  body  of  the  soil  and 
from  which  the  higher  plants,  through  ammonification  and  nit- 
rification, derive  their  necessary  supply  of  nitrogen. 

Legumes  enrich  soil  with  nitrogen.  This  particular  class  of 
plants  to  which  the  clovers,  alfalfas,  vetches,  lupines,  peas,  and 
beans  belong,  is  able,  through  the  agency  of  nodule  forming  bac- 
teria growing  on  the  roots,  to  derive  nitrogen  from  the  inex- 
haustible stores  of  the  atmosphere.  This  peculiar  property  of 


48  Agricultural  Chemistry 

leguminous  plants  is  quite  distinct  from  the  requirements  of  all 
other  farm  crops,  which  acquire  their  nitrogen  from  the  nitrogen 
compounds  already  in  the  soil.  This  fact  is  of  the  greatest  im- 
portance to  agriculture,  for  it  is  "Nature's  principal  method" 
of  increasing  the  nitrogenous  food  in  the  soil.  The  nitrogenous 
compounds  stored  in  such  plants  eventually  become  a  part  of  the 
soil  through  their  decay,  thus  furnishing  food  for  other  plants 
and  increasing  the  fertility  of  the  soil. 

The  constituents  of  soil.  A  popular  and  convenient  classifi- 
cation of  soil  constituents  is  the  following : 

(1)  Sand — mainly  silica,  but  containing  small  fragments  of 
feldspar,  mica,  and  other  minerals. 

(2)  Clay — mainly  kaolin,  but  containing  small  fragments  of 
silica,  feldspar,  etc. 

(3)  Limestone — finely  divided  calcium  carbonate. 

(4)  Humus — the  somewhat  indefinite  nitrogenous  and  carbon- 
aceous material,  brown  or  black  in  color  and  resulting  from  the 
decay  of  plants.     A  brief  description  of  these  materials  will  now 
be  given. 

Sand  is  of  low  specific  heat  and  has  the  lowest  water  retaining 
power  of  all  soil  constituents.  It  is  practically  valueless  as  a 
plant  food,  except  for  the  small  amounts  of  potassium,  calcium 
and  iron  contained  in  the  mineral  fragments  mixed  with  the  true 
sand.  Its  physical  properties  often  have  valuable  effects  upon 
the  character  of  a  soil,  particularly  with  regard  to  friability,  and 
its  relation  towards  water  and  heat. 

Clay  in  its  pure  form  is  free  from  plant  food,  but  is  usually 
well  supplied  with  potash,  because  of  the  feldspar  present.  Com- 
mon clay  contains  quartz  and  calcium  carbonate  (as  in  marls) 
in  addition  to  feldspar.  The  true  clay  (kaolin)  acts  as  a  cement 
to  the  other  mineral  grains. 

It  is  thought  that  even  in  the  purest  clay  there  is  a  small  quan- 
tity of  aluminum  silicate  containing  more  water  than  the  rest, 
to  which  the  plasticity  and  tenacity  of  clay  is  due.  If  this  con- 
stituent is  fully  swollen  with  water  the  clay  is  impervious  and 


The  Soil  49 

sticky,  while  if  it  is  shrunken  or  coagulated  the  clay  becomes 
more  friable  and  less  plastic.  Calcium  compounds  are  partic- 
ularly effective  in  inducing  such  coagulation  and  it  is  to  this 
cause  that  the  improvement  in  texture  of  heavy  clays  by  lime 
application  is  due. 

Limestone.  Calcium  carbonate  is  present  in  the  soil  in  a 
finely  divided  state  distributed  among  the  other  constituents,  but 
in  addition  there  may  be  larger  fragments  which  are  classed  with 
the  "sand."  The  finely  divided  material  is  the  one  of  import- 
ance. It  furnishes  plant  food,  for  the  plant  must  have  calcium, 
but  it  also  plays  other  important  functions.  It  modifies  the 
plasticity  of  clay  in  the  manner  described  above  and  in  addition 
neutralizes  any  acids  accumulating  in  the  soil.  Acids  are  pro- 
duced by  the  decay  and  fermentation  of  vegetable  matter,  and 
if  allowed  to  accumulate,  ivill  render  the  soil  unfit  for  maximum 
crop  production.  Such  soils  are  spoken  of  as  "sour"  and  can 
best  be  restored  to  fertility  by  the  application  of  quick  lime  or 
ground  limestone.  Limestone  performs  another  important  func- 
tion by  acting  as  a  basic  material  necessary  for  the  process  known 
as  nitrification,  to  be  explained  later. 

Limestone  also  serves  an  important  function  in  those  soils 
which  have  received  applications  of  the  commercial  fertilizer, 
ammonium  sulphate.  It  prevents  the  accumulation  of  sulphuric 
acid,  which  otherwise  would  make  the  soil  sour,  by  its  pOAver  to 
neutralize  this  acid.  The  neutral  salt  formed — calcium  sulphate 
— partly  runs  off  in  the  drainage  water. 

Humus  is  the  brown  or  black  organic  matter  of  surface  soils. 
It  is  the  product  formed  by  partial  decay  of  organic  matter  and 
is  the  material  that  gives  the  rich  black  appearance  to  some  soils. 
It  is  formed  from  the  residue  of  plants  previously  grown  on  the 
soil  or  from  added  organic  matter  in  farm  manures  or  commercial 
fertilizers.  It  is  a  mixture  of  many  ill-defined  bodies. 

Recent  researches  show  that  the  so-called  humus  of  the  soil  may 
be  separated  into  a  number  of  classes  of  substances.  Those  com- 
4 


50  Agricultural  Chemistry 

pounds  that  are  extremely  resistant  to  such  solvents  as  ammonia, 
are  still  of  unknown  character  and  probably  constitute  the  more 
permanent  and  inactive  carbonaceous  material  of  the  soil.  That 
portion  of  the  organic  matter  of  the  soil  which  is  soluble  in  alka- 
lies has  been  separated  into  several  groups  of  substances  mostly 
of  known  constitution.  The  group  soluble  in  alkali,  and  pre- 
cipitable  by  acids  from  this  alkaline  solution,  but  insoluble  in 
petroleum  ether  includes  the  resin  acids  and  resin  esters — com- 
plex compounds  of  carbon,  hydrogen,  and  oxygen.  Another 
group,  soluble  in  alkali  and  precipitated  by  acids,  but  soluble  in 
petroleum  ether,  consists  of  fats,  fatty  acids  as  di-hydroxy  stearic 
acid  (C18H3(JO4),  complex  alcohols  as  phytosterol  (C20H44O.H20) 
and  agrosterol  (C26H44O.H20),  and  other  wax-like  substances  as 
paraffinic  acid  (C24H4802)  and  lignoceric  acid  (C24H4802).  That 
group  soluble  in  alkali  but  non-precipitable  by  acids,  contains 
many  of  the  nitrogenous  decomposition  products  of  proteins  and 
nucleins,  and  also  soluble  carbohydrates.  Some  of  the  protein 
decomposition  products — amino  acids — isolated  have  been  histi- 
dine  (C6H902N3)  and  arginine  (C6H14O2N4).  Those  nitrogenous 
products  arising  from  nucleins  and  also  isolated  were  cyto- 
sine  (C4H5ON3H2O),  xanthine  (C5H402N4)  and  hypoxanthine 
(C5H4ON4).  All  this  emphasizes  the  great  complexity  of  the  or- 
ganic matter  of  the  soil.  All  of  these  substances  are  the  decom- 
position products  of  vegetable  tissue  or  specifically  of  its  carbo- 
hydrates, fats,  proteins,  nucleins,  etc.,  and  must  be  the  result  of 
the  combined  hydrolytic,  oxidative  and  reducing  action  brought 
about  by  bacteria,  molds,  and  enzymes  on  the  plant  residues  of 
the  soil.  Some  of  these  substances  isolated  are  but  transient  and 
will  eventually  pass  on  to  those  simple  end  products  such  as  am- 
monia, carbon  dioxide  and  water.  Some  of  these  compounds, 
in  their  transient  stages,  appear  beneficial  to  plant  development, 
while  others  may  act  as  depressants. 

Besides  the  nitrogen  contained  in  humus,  there  is  always  found 
in  its  ash,  such  plant  food  elements  as  phosphorus,  potassium, 
iron  and  sodium,  together  with  silicon  and  aluminum.  These 


-.,  .,  ,  The  Soil  ...  51 

ash  constituents  are  thought  to  be  of  considerable  importance  be- 
cause they  are  apparently  easily  available  to  plants. 

The  humus  of  soils  is  of  the  greatest  agricultural  importance. 
It  not  only  modifies  its  physical  properties,  but  is  the  principal 
storehouse  for  nitrogen.  A  soil  rich  in  humus  is  rich  in  nitro- 
gen; a  soil  poor  in  humus  is  poor  in  nitrogen.  The  plant  does 
not  use  it  directly,  but  its  nitrogen  must  first  be  converted  by 
bacteria  into  water  soluble  forms,  such  as  nitrates,  before  it  is 
available.  By  the  decay  of  humus  the  proportion  of  carbon  diox- 
ide in  the  soil  water  is  increased  and  thus  the  solvent  powers  of 
the  latter  for  plant  food  in  the  mineral  portion  of  the  soil  are 
enhanced. 

Virgin  soils  are  comparatively  rich  in  humus,  but  continuous 
cropping  with  no  return  to  the  soil  of  humus  forming  materials 
may  result  in  its  being  decreased  from  one-third  to  one-half  in 
a  period  of  not  more  than  fifteen  years.  The  amount  of  humus 
in  soils  is  variable,  dependent  upon  such  factors  as  climate  and 
the  previous  soil  treatment.  In  humid  regions  ordinary  arable 
soils  vary  in  humus  content  from  2  to  5  per  cent.  Swampy, 
peaty,  and  muck  soils  contain  larger  amounts.  In  a  bog  soil  the 
per  cent  of  humus  may  be  as  high  as  30  per  cent.  In  arid  re- 
gions the  amount  of  humus  in  the  soil  is  normally  less  than  found 
in  our  humid  regions,  the  amount  rarely  exceeding  1  per  cent, 
but  it  contains  a  high  per  cent  of  nitrogen. 

Physical  properties  of  soils.  These  materials  described  above 
have  great  influence  upon  both  the  physical  and  chemical  prop- 
erties of  soils.  The  important  physical  properties  of  the  con- 
stituents themselves  are  shown  in  the  table  on  page  52. 

The  explanation  of  the  terms  used  in  the  table  are  as  follows : 
Specific  gravity  is  the  weight  of  any  volume  of  the  solid  ma- 
terial compared  with  that  of  an  equal  volume  of  water.  Specific 
heat  (equal  weight)  is  the  ratio  of  the  amount  of  heat  necessary 
to  raise  the  temperature  of  a  certain  quantity  of  a  substance  com- 
pared with  that  required  to  raise  an  equal  weight  of  water 
through  the  same  range  of  temperature.  Specific  heat  (equal 


52 


Agricultural  Chemistry 


volume)  is  the  relative  amounts  of  heat  required  to  raise  equal 
volumes  of  the  material  and  of  water  through  a  given  range  of 
temperature. 

Physical  Properties  of  Soil  Constituents. 


Specific 
Gravity 

Sped  63  Heat 
Equal 
Weight 

Specific  Heat 
Equal 
Volume 

Water  held 
by  100  parts 
by  weight 
of  substance 

Water     

1.00 

1.000 

1.000 

Sand  

2.62 

.189 

.499 

25 

Clav  

2.50 

.233 

.568 

70 

Liruestoi.e  

2.60 

.206 

.561 

85 

Humus  

1.30 

.477 

.587 

181 

From  the  above  table  we  see  that  the  same  quantity  of  heat 
will  raise  1  pound  of  water  and  5  pounds  of  limestone  or  sand 
to  about  the  same  temperature,  or  if  we  consider  only  the  solid 
constituents  of  soil,  the  same  amount  of  heat  will  raise  3  pounds 
of  humus  and  8  pounds  of  sand  to  the  same  temperature. 

Relation  to  heat.  The  sources  of  heat  to  a  soil  are  the  sun  and 
chemical  changes  within  the  soil.  The  chemical  oxidation  of 
organic  matter  in  the  soil  will  slightly  raise  the  temperature,  but 
the  effect  is  generally  slight.  In  an  experiment  at  Tokio,  Japan, 
where  40  tons  of  manure  were  incorporated  with  the  soil  to  a 
depth  of  1  foot,  the  average  temperature  of  the  soil,  after  a  lapse 
of  20  days  was  2.3°  higher  than  that  of  unmanured  soil.  Dur- 
ing the  next  5  days  the  excess  of  temperature  was  only  0.8°. 
Chemical  action  is  at  its  height  during  the  summer  months. 

The  amount  of  heat  received  from  the  sun  and  the  amount  lost 
by  radiation  are  largely  influenced  by  weather  conditions.  Ex- 
tremes of  heat  and  cold  occur  with  a  clear  sky  and  dry  air.  In 
a  cloudy,  moist  climate,  the  variations  in  temperature  are  com- 
paratively small.  At  mid-day  the  power  of  the  sun's  rays  is  at 


The  Soil  53 

its  maximum.  They  then  pass  through  a  minimum  thickness  of 
the  atmosphere.  At  sunrise  they  are  weakened  by  diffusion  over 
a  wide  area  and  in  addition  are  diminished  in  intensity  by  ex- 
cessive atmospheric  absorption.  The  difference  in  the  angle  of 
incidence  of  the  sun 's  rays  is.  the  principal  cause  of  the  difference 
between  a  tropical  climate  and  that  of  Wisconsin.  The  slopes  on 
our  own  fields  often  offer  examples  of  such  effects.  It  is  on  a 
slope  facing  south  that  the  soil  will  reach  its  highest  temperature 
during  sunshine. 

A  dark  colored  soil  becomes  warmer  in  the  sun's  rays  than  a 
light  colored  one,  a  larger  proportion  of  the  sun's  energy  being 
absorbed  and  converted  into  heat.  No  difference  will  be  observed 
on  cloudy  days.  At  night  all  soils  will  cool  to  the  same  point. 

"When  a  soil  is  freely  exposed  to  the  sky  the  temperature  at  the 
surface  will  reach  a  higher  maximum  and  fall  to  a  lower  min- 
imum than  the  air  above  it.  Schuebler  found  that  the  freely  ex- 
posed soil  in  his  garden  at  Tuebingen,  Germany,  averaged  at 
one-twelfth  inch  below  the  surface,  shortly  after  noon  and  in  per- 
fectly clear  weather,  about  120°  Fahr.  for  every  month  from 
April  to  September  inclusive,  and  in  July  reached  146° ;  this 
latter  temperature  was  65°  above  that  of  the  air  taken  at  the 
same  time. 

With  dry  soils,  including  only  hygroscopic  water,  about  3  cubic 
feet  would  be  heated  by  the  sun  to  the  same  degree  as  one  cubic 
foot  of  water.  In  this  condition  there  is  little  difference  between 
different  soils ;  a  dry  peat  will  consume  the  least  heat  and  a  dry 
clay  the  most.  When,  however,  soils  become  wet  great  differ- 
ences appear.  In  a  freshly  drained  condition,  a  coarse  gravel  or 
sand  will  warm  to  a  greater  depth,  while  soils  retaining  more 
water  will  warm  to  a  less  depth.  The  specific  heat  of  wet  peat 
does  not  differ  greatly  from  that  of  its  own  bulk  of  water. 

The  depth  to  which  a  soil  will  be  heated  depends,  however, 
partly  on  the  conductive  power  of  its  constituents.  Sand  has  the 
greatest  power  of  conducting  heat  of  any  soil  constituent.  Air, 
present  in  the  soil,  is  the  worst  conductor.  A  dry  soil  is  thus 


54  Agricultural  -Chemistry 

a  very  poor  conductor  of  heat.  Consolidation  improves  the  con- 
ductivity. Wetting  the  soil  doubles  the  conductivity  of  sand, 
limestone,  or  clay  by  displacing  the  air.  We  see  then,  that  a 
dry,  loose  soil  will  get  very  hot  at  the  surface  when  exposed  to 
the  sun,  but  the  heat  will  penetrate  to  a  slight  depth.  This  ex- 
plains why  gravelly  soils  are  best  suited  for  early  spring  crops. 

Presence  or  absence  of  much  water  is  the  important  factor 
which  chiefly  determines  the  cold  or  warm  character  of  a  soil. 
A  still  more  potent  reason  for  the  coldness  of  wet  soils,  is,  how- 
ever, the  losst>f  heat  during  evaporation.  When  a  pint  of  water 
is  removed  by  evaporation  from  97  pints,  the  96  remaining  pints 
will  have  fallen  10°  Fahr.  in  temperature  unless  this  amount  of 
heat  has  been  supplied  from  some  external  source.  Undrained 
meadows  and  heavy  clays  consequently  are  cold  soils  because 
much  of  the  sun 's  heat  is,  in  these  cases,  consumed  in  evaporating 
water.  Parks  found  that  an  undrained  peat  bog  30  feet  deep, 
had  a  temperature  of  46°  when  measured  below  a  distance  of 
1  foot  from  the  surface.  In  the  middle  of  June  he  found  the 
temperature  47°  at  7  inches  below  the  surface,  while  the  drained 
portion  had  a  temperature  of  66°  at  this  depth,  and  a  tempera- 
ture of  50°  at  2  feet  below  the  surface.  Draining  is  the  only 
cure  for  a  cold,  wet  soil. 

The  temperature  of  the  subsoil  is  practically  constant  through- 
out the  year  at  a  certain  distance  from  the  surface.  Observations 
at  Greenwich  Observatory,  England,  in  a  well  drained  gravel, 
showed  that  the  variations  of  day  and  night  are  slightly  felt  at 
3  feet  from  the  surface.  At  25^  feet  the  maximum  temperature 
usually  occurs  in  the  latter  part  of  November  and  the  minimum 
in  the  first  week  in  June.  The  difference  between  the  two  is 
about  3°.  These  observations  make  it  clear  that  the  soil  and 
subsoil  are  generally  warmer  than  the  air  in  autumn  and  cooler 
than  the  air  in  spring. 

Tenacity  of  soil.  The  tenacity  of  a  heavy  soil  is  due  to  the 
fine  silt  and  clay.  The  coarser  elements  of  a  soil,  such  as  a  fine 
sand,  exhibit  little  cohesion.  Clay  owes  its  cementing  power  it 


The  Soil  55 

is  believed,  to  the  presence  of  a  small  quantity  of  a  hydrated  col- 
loid (jelly-like)  body,  which  according  to  Schloesing  rarely  ex- 
ceeds 1.5  per  cent  of  the  clay.  The  remainder  of  the  clay  is  com- 
posed of  extremely  fine,  solid  particles.  In  the  purest  natural 
clays,  all  the  constituents  have  the  same  general  chemical  com- 
position, that  is,  they  are  hydrated  silicates  of  aluminum ;  but  in 
soils  the  non-colloid  constituents  of  the  clay  may  be  of  a  very 
various  nature.  In  brick  clay  this  material  is  quartz  sand;  in 
marl  it  is  limestone. 

The  condition  of  clay  soils  depends  much  on  whether  the  clay 
is  coagulated  or  not.  When  the  clay  is  uncoagulated,  the  soil  is 
sticky,  impervious  to  water,  and  cannot  be  reduced  to  a  fine  tilth. 
When  a  clay  is  coagulated  the  soil  has  a  granular  structure,  is 
pervious  to  water,  and  can  be  reduced  to  powder.  It  is  coagu- 
lated by  lime  and  by  many  salts,  and  especially  by  salts  of  cal- 
cium. Colloid  clay  will  remain  permanently  suspended  in  dis- 
tilled water.  It  is  precipitated  by  the  addition  of  a  small  quan- 
tity of  a  calcium  salt.  An  application  of  lime  to  clay  soils  is; 
well  known  to  be  extremely  effective  in  diminishing  their  ten- 
acity, rendering  them  pervious  to  water,  and  more  easy  of  tillage. 
In  cultivated  sandy  soils  humates  are  often  of  great  value  as 
cementing  materials;  these,  like  true  clay,  are  colloid  bodies. 
Schloesing  found  that  1  per  cent  of  a  humate,  as  calcium  humate,, 
was  as  effective  as  a  cement  for  sand  as  11  per  cent  of  clay. 
Humates,  however,  will  lose  their  cementing  power  on  drying, 
while  clay  will  not.  The  improvement  of  the  texture  of  sandy 
soils  by  the  continued  use  of  farm  yard  manure,  or  by  the  plow- 
ing under  of  green  crops,  is  a  fact  familiar  to  the  farmer.  While 
applications  of  humus  forming  materials,  as  the  above,  increase 
the  coherence  of  sand,  they  have  an  opposite  effect  on  clay,  and 
are  the  most  effectual  means  at  the  disposal  of  the  farmer  for 
lightening  a  heavy  soil.  Lime  will  also  tend  to  increase  the  co- 
herence of  sand. 

Relation  to  water.    We  have  learned  that  a  good  soil  consists 
of  solid  particles  of  fairly  uniform  size.     The  spaces  between 


56  Agricultural  Chemistry 

these  particles  constitute  about  40  per  cent  of  the  volume.  If 
the  particles  are  a  mixture  of  large  and  small,  as  for  example 
gravel  and  sand,  the  volume  of  these  spaces  is  much  reduced.  On 
the  other  hand  if  the  particles  are  themselves  porous,  as  in  the 
case  of  chalk,  loam,  and  especially  humus,  then  the  volume  of 
the  spaces  is  increased.  It  is  this  volume  of  the  inter-spaces 
which  determines  the  amount  of  water  which  a  soil  will  contain 
when  perfectly  saturated,  or  the  amount  of  air  which  it  will  con- 
tain when  dry. 

Humus  increases  the  capacity  for  a  soil  to  absorb  and  retain 
water  and  consequently  a  crop  grown  on  a  soil  containing  a  fair 
amount  of  humus  is  less  likely  to  suffer  from  drought.  The  fol- 
lowing -table  illustrates  this  point.  It  gives  the  amount  of  water 
held  by  1  cubic  foot  of  different  varieties  of  soil ; 

Los.  of  water  in 
Kinds  of  Soil  1  cubic  foot 

Sand 27.3 

Sandy  Clay 38.8 

Loam    41.4 

Humus  50.1 

Farm  crops  will  not  grow  in  a  soil  permanently  saturated  with 
water  and  from  which  air,  consequently,  is  excluded;  the  best 
growth  is  obtained  from  soils  one-half  or  two-thirds  saturated. 
The  surface  of  a  soil  is  seldom  saturated,  except  immediately 
after  a  heavy  rain ;  it  is  the  quantity  of  water  which  a  soil  will 
retain  when  fully  drained  which  determines  its  capacity  for  sup- 
plying a  crop  with  water.  The  amount  of  water  permanently 
retained  by  a  soil  does  not  depend  upon  the  volume  of  the  inter- 
spaces, but  upon  the  extent  of  internal  surface,  the  water  being 
held  by  adhesion  as  a  film  on  the  surface  of  the  particles.  The 
smaller,  therefore,  the  particles  of  a  soil,  or  the  more  porous,  the 
greater  is  the  amount  of  water  retained.  Two  samples  of  pow- 
dered quartz,  one  coarse,  the  other  very  fine,  will  hold  when 
saturated,  more  than  40  per  cent  of  their  volume  as  water.  But 
when  drained,  the  coarse  sand  will  retain  about  7  per  cent  while 


The  Soil  57 

the  fine  quartz  holds  44.6  per  cent  of  water.  The  latter  will 
loose,  in  fact,  no  water  by  drainage. 

Gravels  and  coarse  sand  retain  the  least  water  when  drained. 
As  the  particles  become  smaller,  the  retention  of  water  increases. 
Colloids,  jelly-like  bodies,  as  clay  and  humus,  increase  the  power 
of  retaining  water,  as  such  bodies  swell  up  when  wetted  and  hold 
the  water  in  jelly-like  substances.  The  addition  of  humus  to 
soils  is  one  of  the  best  ways  of  increasing  their  water  retaining 
capacity. 

Water  from  below  may  supply  a  surface  soil  if  a  saturated  sub- 
soil exists  at  a  moderate  distance.  Such  water  is  said  to  be 
raised  by  capillary  action,  which  simply  means  that  the  surfaces 
of  the  soil  particles  exert  an  attraction  for  water.  The  finer  the 
particles  and  the  closer  they  are  packed,  the  greater  the  height  to 
which  water  will  be  carried  by  capillary  action.  When  the  dis- 
tance it  has  to  travel  increases,  the  quantity  reaching  the  surface 
diminishes.  When  the  fineness  of  the  particles  exceeds  a  certain 
point  the  quantity  of  water  raised  also  diminishes.  It  is  not 
always  the  soil  with  the  finest  particles  that  brings  most  water 
to  the  surface.  There  is  a  certain  degree  of  fineness  of  soil  par- 
ticles that  acts  most  effectively.  Capillary  action  is  seldom  able 
to  maintain  a  sufficient  water  supply  at  the  surface.  In  Wiscon- 
sin every  few  years  crops  suffer  from  drought,  although  a  per- 
manent water  supply  exists  several  feet  below  the  surface.  Cap- 
illary action  is  most  effective  in  the  case  of  silty  soils ;  such  soils 
were  deposited  from  running  water  and  consist  of  very  uniform 
particles,  but  without  any  true  clay.  Some  western  soils,  which 
are  capable  of  growing  wheat  with  a  winter  rainfall  of  10  to  12 
inches  and  a  continuous  summer  drought  of  three  months'  dura- 
tion, are  deep,  fine  grained,  and  uniform,  with  practically  no 
particles  of  the  fineness  of  clay  to  check  the  upward  lift  of 
capillarity. 

The  evaporation  from  a  saturated  soil  is  greater  than  from  a 
water  surface  and  as  the  soil  drys  the  rate  of  evaporation  rapidly 
diminishes.  The  average  annual  evaporation  from  a  bare  loam 


58  Agricultural  Chemistry 

at  Madison,  Wisconsin,  is  about  fifteen  inches.  While  soils  of 
various  character  evaporate  equal  amounts  while  saturated,  they 
exhibit  great  differences  as  drying  proceeds.  A  soil  of  coarse 
particles  and  loose  texture  dries  quickest  and  to  the  greatest 
depth.  Consequently  it  appears  to  be  good  practice  to  avoid 
deep  tillage  in  .early  summer,  if  land  is  intended  to  carry  a  crop. 

Evaporation  from  the  soil  is  diminished  by  protection  from 
sun  and  wind.  Economy  of  water  is  best  effected  by  mulching 
with  straw.  Keeping  the  surface  stirred  to  a  depth  of  an  inch 
or  two,  thus  providing  a  mulching  of  loose  dry  soil,  is  an  excel- 
lent practice  and  forms  a  fundamental  part  of  successful  culti- 
vation in  dry  climates. 

The  greatest  evaporation  of  water  takes  place  from  the  soil 
ivhen  it  grows  a  crop.  The  water  in  a  soil  growing  barley  and 
in  an  adjacent  bare  fallow  was  determined  at  Rothamsted,  Eng- 
land, at  the  end  of  June  during  the  drought  of  1870.  It  was 
found  that  down  to  54  inches  below  the  surface  the  barley  soil 
contained  9  inches  less  water  than  the  fallow  soil.  The  injurious 
effect  of  weeds  in  the  summer  time  is  largely  due  to  their  robbing 
the  soil  of  water. 

With  dry  soils  the  farmer  should  aim  to  increase  the  amount 
of  humus.  Crops  should  be  sown  early  and  the  land  kept  solid ; 
very  shallow  summer  cultivation  should  be  resorted  to.  Such 
land  majr  possess  distinct  advantages.  It  furnishes  the  earliest 
crops  to  market  gardeners,  the  soil  being  easily  warmed.  A  little 
rain  will  wet  it  to  a  considerable  depth  and  the  whole  of  the 
water  it  contains  is  available  to  plants. 

A  soil,  when  drained,  is  seldom  too  wet  because  of  its  power  to 
retain  water.  The  trouble  is  more  often  due  to  want  of  drain- 
age ;  the  remedy  for  such  a  soil  is  deep  tillage  and  draining.  Ap- 
plications of  lime  or  an  increase  in  the  humus  content  may  be 
an  effective  means  of  rendering  the  surface  soil  more  pervious  to 
water. 

The  wettest  soil  does  not  always  supply  the  largest  amount  of 
water  to  a  crop.  A  peaty  soil  holds  most  water,  but  it  is  held 


-The  Soil  59 

so  firmly  by  the  colloid  matter  as  to  be  unavailable  to  plants.  A 
stiff  clay  fails  in  a  drought  as  the  water  in  this  class  of  soils  is 
also  firmly  held  and  moves  with  difficulty.  Soils  composed  of 
silt  or  extremely  fine  sand  are  those  which  yield  water  most  effec- 
tually to  a  growing  crop. 

Chemical  changes  occurring  in  soils.  The  chemical  changes 
going  on  in  soil  are  numerous  and  complex.  The  mineral  matter 
is  subjected  to  the  same  influences  as  led  to  its  breaking  down  in 
the  formation  of  soil  from  the  original  rock.  These  changes  are, 
however,  hastened  because  of  the  great  quantity  of  carbon  di- 
oxide produced  by  the  decay  of  organic  matter.  Fragments  of 
feldspar  are  decomposed  with  formation  of  silicic  acid,  potassium 
carbonate  and  kaolin  or  clay,  according  to  the  following  equa- 
tion :— 

Al203.K20.6Si02+CO2+10H20=Al2O3.2SiO2.2H20-f-K2C03 
bfthoclase  carbon    Water  clay  potassium 

dioxide  carbonate 

+4H4Si04 
.  silicic  acid 

The  clay  remains  behind,  but  the  silicic  acid  and  potassium 
carbonate  may  in  part  be  dissolved :  and  either  carried  away  in 
the  drainage,  or  may  be  absorbed  by  the  roots  of  plants  or  by 
some  of  the  absorptive  constituents  of  soils.  Calcium  carbonate 
or  limestone  is  dissolved  by  water  containing  carbon  dioxide, 
which  is  true  of  all  soil  waters,  and  is  in  part  carried  away  in 
the  drain  or  absorbed  by  certain  soil  constituents. 

Calcium  phosphate,  as  it  exists  in  minerals,  is  nearly  insoluble 
in  water,  but  through  the  action  of  the  soil  water  containing 
carbon  dioxide  in  solution,  it  is  changed  to  more  soluble  forms 
and  therefore  becomes  available  to  plants : — 

Ca3  (POJ  2+2C02+2H20=Ca2H2  (P04)  2+Ca  (HCO3)  2 
tri-calcium    carbon  di'Calcium  calcium  acid- 

phosphate     dioxide  phosphate  carbonate 

In  contact  with  certain  forms  of  iron  and  aluminum  in  the  soil 
the  soluble  calcium  phosphates  may  be  changed  to  iron  and  alu- 


60  Agricultural  Chemistry 

minum  phosphates  and  held  back  in  the  soil  in  finely  divided  con- 
dition, and  though  then  quite  insoluble  in  water,  may  still  be  dis- 
solved by  the  acid  juices  of  the  plant's  roots. 

Absorption  of  soluble  plant  food  by  soils.  If  the  plant  food 
made  soluble  by  the  chemical  changes  occurring  in  soils  were  not 
retained  by  the  absorptive  power  of  the  latter  the  depletion  of 
fertility  would  go  on  at  a  much  more  rapid  rate  than  it  actually 
does.  Most  soils  contain  substances,  which  have  the  power  of 
uniting  with  potassium,  ammonium,  and  to  a  less  extent  with 
calcium  compounds  and  with  phosphates,  converting  them  into 
insoluble  forms.  If  a  solution  containing  phosphoric  acid,  potash 
or  ammonia  is  poured  upon  a  sufficiently  large  quantity  of  fer- 
tile soil,  the  water  which  filters  through  will  be  found  nearly 
destitute  of  these  substances.  This  retentive  power  of  a  soil  is 
of  the  greatest  agricultural  value  as  it  enables  it  to  maintain  its 
fertility  when  washed  by  rain  and  permits  of  the  economic  use 
of  many  soluble  manures.  Ferric  oxide,  a  common  ingredient  of 
soil  and  one  to  which  the  red  color  of  many  soils  is  due,  will  re- 
tain and  fix  any  soluble  phosphate.  When  a  solution  of  phos- 
phate of  calcium  in  carbon  dioxide  is  placed  in  contact  with  an 
excess  of  hydrated  ferric  oxide,  the  phosphoric  acid  is  gradually 
absorbed. and  the  calcium  left  in  solution  as  a  carbonate.  Hy- 
drated alumina  acts  in  the  same  way.  Ferric  oxide  and  alumina 
have  also  a  retentive  power  for  ammonia,  potash  and  other  bases, 
but  the  compounds  formed  are  more  or  less  decomposed  by  water. 

The  permanent  retentive  power  of  soils  for  potash  and  other 
bases  is  chiefly  due  to  the  hydrous  double  silicates. 

Humus  has  a  great  absorptive  power  for  ammonia.  It  also  re- 
tains other  bases  with  which  it  can  form  insoluble  compounds. 

Magnesia,  lime  and  soda  are  retained  by  the  soil,  but  in  a 
less  powerful  manner  than  are  potash  and  ammonia.  When  a 
solution  of  a  salt  of  potassium  or  ammonium  is  placed  in  contact 
with  a  fertile  soil,  lime  will  come  into  solution  and  take  the  place 
of  the  potash  or  ammonia,  which  is  by  preference,  absorbed. 

Soils  destitute  of  lime  retain  very  little  potash  or  ammonia 


Tlie  Soil  61 

Avhen  these  are  applied  as  salts  of  powerful  acids,  as  for  instance, 
as  chlorides,  nitrates,  or  sulphates.  When  carbonate  of  calcium 
is  present  the  potassium  or  ammonium  salt  is  decomposed,  the 
base  is  retained  by  the  soil,  while  the  acid  escapes  into  the  drain- 
age water  united  with  calcium.  This  is  illustrated  in  the  fol- 
lowing equation : 

CaC03     +     2KC1    =    CaCl2     -f     K2C03 
calcium        potassium          calcium          potassium 
carbonate        chloride  chloride          carbonate 

The  addition  of  marl  or  limestone  may  thus  greatly  increase  the 
retentive  power  of  a  soil  for  bases.  The  bases  absorbed  by  the 
soil  may  be  slowly  removed  by  the  action  of  water.  This  of 
course  occurs  to  the  least  degree  in  a  soil  that  has  absorbed  little 
or  has  been  already  washed,  and  is  greatest  in  a  soil  that  has  been 
heavily  manured. 

The  permanent  fertility  of  a  soil  is  closely  connected  with  its 
power  of  retaining  plant  food.  In  soils  containing  clay,  only 
traces  of  phosphoric  acid,  ammonia  or  potash  are  ever  found  in 
the  drainage  water.  Sandy  soils,  from  their  smaller  chemical 
retentive  power  and  free  drainage,  are  of  less  natural  fertility 
and  much  more  dependent  on  immediate  supplies  of  plant  food. 

There  can  be  little  doubt  that  the  active  plant  food  contained 
in  a  soil,  which  is  capable  of  being  taken  up  by  roots,  exists 
either  in  solution  or  in  the  states  of  combination  just  referred 
to — that  is,  in  union  with  ferric  oxide,  hydrous  silicates  or  hu- 
mus. Different  crops  have  very  different  powers  of  attacking 
these  various  forms  of  plant  food. 

Ammonification  and  nitrification.  Perhaps  the  most  import- 
tant  reactions  going  on  in  a  soil  are  those  connected  with  the 
decay  of  organic  matter  and  the  changes  in  the  state  of  combina- 
tion of  the  nitrogen.  The  organic  matter  is  continually  being 
oxidized,  the  carbon  being  mainly  converted  into  carbon  dioxide. 
The  material  from  which  the  nitrogenous  matter  of  soils  is  de- 
rived contains  always  a  large  proportion  of  carbon.  In  the  roots 
and  stubble  of  cereal  crops  the  relation  of  nitrogen  to  carbon  is 


62  Agricultural  Chemistry 

about  1 :43 ;  in  those  of  leguminous  crops  1 :23 ;  in  moderately 
rotted  farm  manure  1 :38.  In  an  aerated  soil  these  materials  are 
oxidised  by  the  action  of  various  organisms  (worms,  fungi,  and 
bacteria)  and  large  quantities  of  carbon  dioxide,  produced.  As 
a  result  of  this  loss  of  carbon,  we  find  that  the  surface  soil  of  a 
pasture  (roots  removed)  will  contain  about  1  part  of  nitrogen  to 
13  of  carbon ;  the  surface  soil  of  an  arable  field  1 :10,  and  a  clay 
soil  1:6.  These  figures  represent  the  proportion  of  nitrogen  to 
carbon  in  the  commonest  forms  of  humus  matter.  Humus  repre- 
sents merely  a  stage  in  the  decomposition  of  organic  matter;  in 
the  end  the  whole  of  the  carbon,  hydrogen  and  nitrogen  appear 
as  carbon  dioxide,  water  and  ammonia  or  nitrates. 

The  nitrogen  contained  in  humus  is  not  in  a  condition  to  serve 
as  food  for  ordinary  crops.  The  gradual  decomposition  of  soil 
humus  is  consequently  generally  essential  to  fertility.  This 
change  in  the  humus  is  brought  about  by  fungi  and  bacteria, 
which  convert  the  nitrogen  of  organic  matter  first  into  ammo- 
nia— ammonification — and  then  into  nitrates,  forms  which  are 
soluble  in  water  and  available  to  the  plant.  The  final  nitrifica- 
tion of  ammonia  is  performed  by  two  species  of  bacteria,  one  of 
which  produces  nitrites,  which  the  other  changes  into  nitrates. 
Fresh  plant  residues  are  more  easily  nitrified  than  old  humus 
matter,  but  nitrification  does  not  begin  until  the  earlier  stages  of 
decomposition  have  occurred. 

The  type  reactions  involved  in  nitrification  may  be  represented 
by  the  following  equations : 

CO(NH2)2     +     2H20    =        (NH4)2C03 

urea  water  ammonium  carbonate 

'(NH4)2C03+302=C02+2HN02+3H2O 
ammonium  oxygen  carbon  nitrous        water 
carbonate  dioxide      acid 

CaC03+2HN02=Ca(N02)2+C02+H20 
calcium     nitrous          calcium      carbon  water 
carbonate    acid  nitrite      dioxide 

Ca(N02)2     +     02    =    Ca(N03)2 
calcium  nitrite        oxygen        calcium  nitrate 


.,,..-..„  .TheSo.il  63 

The  nitrifying  organisms  occur  most  abundantly  in  the  surface 
soil;  the  depth  to  which  their  action  extends  depends  on  the 
porosity  of  the  soil.  In  experiments  at  Rothamsted,  England, 
on  a  clay  subsoil,  it  was  found  that  the  organisms  did  not  always 
occur  in  samples  of  the  soil  taken  at  more  than  3  feet  below  the 
surface. 

Nitrification  only  takes  place  in  a  moist  soil  and  one  sufficiently 
porous  to  admit  air.  It  is  always  necessary  that  some  base 
should  be  present  with  which  the  nitric  acid  formed  may  com- 
bine. This  condition  is  usually  fulfilled  by  the  presence  of  car- 
bonate of  lime.  Lack  of  oxygen  and  an  acid  condition  of  the 
soil  are  both  unfavorable  to  the  growth  of  nitrifying  organisms. 
This  gives  us  a  rational  explanation  of  the  advantages  of  thor- 
ough tillage  which  aerates  the  soil  and  of  the  maintenance  of 
non-acid  soils  by  the  application  of  lime.  Nitrification  is  most 
active  in  the  summer  season;  it  ceases  near  the  freezing  point. 
The  nitrifying  organisms  may  be  killed  by  severe  drought. 

The  oxidation  of  humus  not  only  makes  the  nitrogen,  which 
it  contains,  available  to  plants,  but  it  also  liberates  the  ash  con- 
stituents combined  with  the  humus  and  enables  them  to  take  part 
again  in  the  nourishment  of  the  growing  crop. 

Oxidation  is  most  active  in  soils  under  tillage.  In  arable  land 
the  production  of  available  plant  food  is  at  its  maximum  and 
so  is  also  the  waste  by  drainage.  The  nitrogenous  humus  matter 
of  tilled  land  is  maintained  only  when  the  new  supply  from  crop 
residues  and  organic  manures  is  equal  to  the  amount  annually 
oxidized.  In  an  untilled  pasture  or  forest  soil,  on  the  other  hand, 
a  considerable  accumulation  of  organic  matter  may  take  place, 
the  annual  residue  of  dead  leaves  and  roots  being  often  in  excess 
of  the  amount  oxidized. 

In  a  peat  bog  oxidation  is  further  checked  by  the  high  water 
level,  which  excludes  air  from  the  soil ;  under  such  conditions  an 
unlimited  accumulation  of  organic  matter  may  take  place  if 
plants  capable  of  growing  under  these  circumstances  are  present. 

Denitrification.     "When  a  soil  is  not  in  an  aerated  condition, 


64  Agricultural  Chemistry 

but  has  the  spaces  between  the  particles  filled  with  water,  the 
nitrates  present  are  destroyed  by  certain  kinds  of  bacteria,  the 
oxygen  of  the  nitrate  combining  with  carbon  to  form  carbon 
dioxide,  while  the  nitrogen  is  set  free  and  returned  to  the  air 
in  its  elemental  condition.  If  a  soil  be  consolidated,  water- 
logged or  highly  charged  with  oxidizable  carbonaceous  matter, 
the  conditions  become  favorable  for  denitrification.  Conditions 
favorable  to  nitrification,  such  as  a  plentiful  supply  of  oxygen 
and  absence  of  acidity,  are  those  unfavorable  to  denitrification, 
so  that  the  farmer  in  producing  proper  conditions  for  the  former 
desirable  process  is  at  the  same  time  preventing  the  injurious 
denitrification.  The  application  of  very  large  dressings  of 
manure,  along  with  nitrate  of  soda,  sometimes  causes  a  consid- 
erable loss  of  nitrogen  from  this  process  of  denitrification. 

The  reaction  expressing  this  loss  of  free  nitrogen  has  been 
formulated  by  Gayon  as  follows: 

5C6H12O6+24KNO3=24KHC03+6C02+18H2O+12N2 
sugar  nitrate  nitrogen 

Fixation  of  atmospheric  nitrogen  in  soils.  Besides  the  or- 
ganisms associated  with  leguminous  plants  and  which  assimilate 
atmospheric  nitrogen  freely  when  in  union  with  the  roots  of  the 
host  plant,  there  are  bacteria  in  the  soil  which  use  free  nitrogen, 
but  which  do  not  grow  in  union  with  the  higher  plants.  These 
bacteria — azotobacter — are  found  in  most  soils  and  are  said  to 
possess  this  power  when  the  supply  of  carbonaceous  matter  in  the 
soil  is  plentiful.  Indeed,  some  years  ago,  such  organisms  under 
the  name  of  "alinite"  were  prepared  for  sale,  but  the  success 
attending  their  use  was  doubtful  and  their  manufacture  has 
ceased. 

It  is  thought  that  fertility  and  richness  in  nitrogen  of  forest 
or  prairie  soil  is  largely  due  to  the  activity  of  such  organisms, 
which  would  find  suitable  conditions  for  growth  in  the  large 
quantity  of  organic  carbonaceous  matter  contained  in  such  soils. 
At  present  it  is  impossible  to  say  whether  the  nitrogen  added  to 
the  soil  in  this  way  is  of  any  considerable  amount. 


The  Soil  65 

Gases  in  a  soil.  The  spaces  between  the  particles  of  soil,  be- 
sides containing  a  certain  amount  of  moisture,  are  usually  oc- 
cupied by  air.  Because  of  the  chemical  changes  going  on  in  the 
soil  this  air  becomes  robbed  of  its  oxygen,  and  enriched  with 
carbon  dioxide.  This  air  is  not  stagnant  but  undergoes  constant 
renewal  by  diffusion  from  the  air  above. 

The  gases  drawn  from  the  soil  at  different  times  will  be  found 
to  vary  in  composition ;  the  oxygen  may  be  anywhere  from  10  to 
20  per  cent,  the  carbon  dioxide  from  1  to  10  per  cent,  while  the 
nitrogen  usually  differs  very  little  in  amount  from  that  in  the 
atmosphere,  that  is,  about  78  per  cent.  The  amount  of  carbon 
dioxide  is  greater  and  of  oxygen  less  during  the  summer  and 
autumn  than  in  the  winter  or  spring.  The  higher  temperature 
in  the  soil  during  summer  and  autumn  favors  chemical  de- 
composition, with  greater  production  of  carbon  dioxide. 

Tillage  and  drainage.  The  operations  of  tillage  and  drain- 
age serve  in  many  important  ways  to  make  the  conditions  for 
plant  life  more  favorable  and  to  increase  the  amount  of  plant 
food  wiii eh  is  at  the  disposal  of  the  crop. 

By  tillage  the  surface  soil  is  pulverized  and  brought  into  a 
loose,  open  condition.  Large  lumps  are  broken  into  small  par- 
ticles and  the  fine  tilth  thus  obtained,  allows  a  rapid  extension 
of  the  delicate  root  fibers  and  consequently  greater  room  for  root 
growth.  It  increases  the  surface  to  which  the  roots  are  exposed 
and  necessarily  gives  the  developing  plant  a  larger  feeding  area. 

Tillage  hastens  chemical  changes  in  the  soil  by  bringing  to- 
gether particles  which  have  not  before  been  in  contact.  Par- 
ticles with  different  chemical  properties  are  thus  enabled  to  act 
upon  each  other. 

The  changes  induced  by  freezing  and  thawing  may  also  be 
greatly  increased  by  proper  tillage.  Fall  plowing  exposes  the 
large  lumps  to  the  influence  of  the  weather  during  the  winter. 
This  disintegrates  the  clods  and  improves  some  classes  of  soils 
in  a  remarkable  manner.  It  also  tends  to  save  the  moisture,  as 
5 


66  Agricultural  Chemistry 

the  loose  ground  turned  up  by  the  plow  prevents  loss  of  water 
by  evaporation.  The  broken  uneven  surface  also  favors  a  greater 
absorption  by  the  soil  of  the  winter  rain  or  snow.  In  an  ex- 
periment at  the  Wisconsin  Station,  a  plot  plowed  in  the  fall  con- 
tained 1.15  acre  inches  more  water  than  an  adjacent  plot  not 
so  plowed.  It  must  be  remembered  that  fall  plowing  may  not 
ahvays  be  the  best  practice,  as  hard  soils,  low  in  humus,  may  be 
badly  puddled  if  fall  plowed.  Plowing  the  ground  very  early  in 
the  spring  is  a  rational  practice,  for  there  is  no  other  season  when 
tillage  is  so  effective  in  conserving  the  soil  moisture.  Experi- 
ments indicate  that  in  soils  where  such  practice  has  been  fol- 
lowed, the  moisture  content  will  be  greater  than  in  those  un- 
plowed.  Judgment  must  be  exercised,  however,  in  the  choice 
of  time  in  order  that  no  injury  to  the  texture  may  follow. 

By  the  action  of  the  plow,  the  residues  of  crops,  weeds  and 
manures  are  buried,  and  incorporated  with  the  soil.  The  deep 
tillage  of  heavy  land  allows  rain  to  penetrate  it  and  establishes 
the  drainage  of  the  surface  soil,  and  increases  the  temperature. 

A  shallow  surface  tillage  preserves  the  moisture  of  the  soil  in 
time  of  drought.  It  lessens  the  evaporation  from  the  surface  by 
breaking  the  capillary  connection  with  the  store  of  water  below 
the  surface.  After  a  rain  this  will  be  again  established  and  the 
cultivation  should  be  repeated  as  soon  as  possible.  Such  a 
surface  layer  of  dry  soil  is  called  an  "earth  mulch"  and  serves 
the  same  purpose  as  a  covering  of  straw  or  like  material. 

Another  important  result  of  tillage  is  that  the  soil  is  thoroughly 
exposed  to  the  influence  of  the  air.  The  nitrification  processes 
are  greatly  facilitated,  with  the  production  of  nitrates  and  car- 
bon dioxide.  The  disintegration  and  solution  of  mineral  par- 
ticles will  take  place  from  the  mechanical  and  chemical  actions 
brought  into  play.  It  will  also  prevent  the  formation  of  such 
compounds  as  sulphide  of  iron,  known  to  be  injurious  to  vege- 
tation. Oxygen  is  also  necessary  for  the  germination  of  seeds, 
and  the  aeration  of  soils  by  tillage  is  necessary  for  this  im- 
portant start  in  the  plant's  development. 


The  Soil  67 

By  means  of  tile  drainage  the  many  chemical  reactions  going 
on  in  a  soil  are  carried  down  to  a  greater  or  less  extent  into  the 
subsoil;  for  as  the  water  level  is  lowered  the  air  enters  from 
above  to  fill  the  spaces  in  the  soil.  By  drainage,  the  depth  to 
which  the  roots  penetrate,  and  consequently  the  extent  of  their 
feeding  ground,  is  increased.  This  helps  them  to  withstand 
drought.  They  will  not  be  so  easily  affected  by  the  extreme  dry- 
ing of  the  surface  of  the  soil  that  takes  place  in  times  of  little 
rainfall.  Roots  will  not  grow  in  the  absence  of  oxygen  and  will 
rot  as  soon  as  they  reach  a  permanent  water  level. 

In  a  water-logged  soil  denitrification  is  active  and  nitrates 
present  are  destroyed,  a  part  of  the  nitrogen  being  evolved  as 
elemental  nitrogen  and  returned  to  the  atmosphere.  The  soil 
may  in  this  way,  suffer  a  considerable  loss  of  plant  food  by  lack 
of  drainage. 

Losses  caused  by  drainage.  The  water  draining  from  land 
always  carries  with  it  dissolved  matter.  The  substances  chiefly 
removed  by  the  water  will  be  calcium  carbonate,  and  the  nitrates, 
chlorides  and  sulphates  of  calcium  and  sodium.  When  heavy 
rain  falls  these  substances  are  washed  into  the  subsoil  and  partly 
escape  by  the  nearest  outfall  into  the  springs,  brooks  and  rivers. 
The  loss  of  nitrates  during  a  wet  season  may  be  very  consider- 
able. The  loss  is  greatest  from  uncropped  soil  for  several  rea- 
sons: 

(1)  Because  of  the  greater  amount  of  drainage. 

(2)  Because  no  absorption  of  nitrates  by  the  roots  of  plants 
takes  place. 

(3)  Because  the  land,  when  free  from  crops,  dries  more  slowly 
allowing  nitrification  to  proceed  for  a  longer  time. 

The  average  loss  of  nitrogen  as  nitrates  from  uncropped  soil 
at  Rothamsted,  England,  for  20  years,  wras  33.8  pounds  per  acre 
which  is  equal  to  216  pounds  of  commercial  nitrate  of  soda.  The 
loss  will  vary  greatly  with  the  nature  of  the  soil.  When  the  land 
is  under  crop  this  loss  of  nitrates  by  drainage  is  greatly  reduced. 
these  being  constantly  taken  up  by  the  roots  and  employed  as 


68 


Agricultural  Chemistry 


plant  food.  In  an  experiment  at  Grignon,  France,  the  yearly 
loss  of  nitrogen  per  acre  on  a  soil  bearing  rye  grass  was  but 
2.3  pounds. 

The  losses  of  calcium  carbonate  vary  considerably,  dependent 
upon  the  nature  of  the  soil.     From  soils  of  igneous  origin  its 


Showing  washing  and  loss  of  fertility  where  the  soil  has  been  left  bare. 

amount  has  been  estimated  at  500  pounds  per  acre  per  year, 
while  from  limestone  soils  the  loss  has  been  estimated  at  as  much 
as  2700  pounds  per  acre.  The  amount  lost  is  increased  when 
ammonium  compounds  are  used  as  fertilizer. 


The  Soil  69 . 

The  loss  of  phosphoric  acid  is  probably  very  small,  except  in 
the  case  of  peaty  soils,  which  though  often  very  deficient  in  this 
constituent  generally  lose  much  in  the  drainage.  This  is  prob- 
ably due  to  the  presence  of  vegetable  acids  and  carbon  dioxide 
produced  by  the  decay  of  organic  matter,  which  would  intensify 
the  solvent  action  of  water.  German  experiments  report  an 
annual  loss  per  acre  of  from  about  8  pounds  for  clay  soils  to 
19.6  pounds  for  peaty  soils. 

The  loss  of  potash  is  variable,  but  small  in  amount.  From  ex- 
periments at  Rothamsted,  the  annual  losses  in  potash  per  acre 
were  found  to  vary  from  3  to  12  pounds.  The  losses  of  sulphur 
by  drainage  from  soils  may  be  considerable.  At  Rothamsted  it 
was  found  that  about  50  pounds  per  acre  per  year  of  sulphur, 
calculated  as  sulphur  trioxide,  escaped  into  the  drainage  water. 

Highly  manured  land  will  sustain  larger  absolute  losses  of 
plant  food  than  lands  in  an  average  state  of  fertility. 

Soil  as  a  source  of  plant  food.  The  proportion  of  plant  food 
present  in  soils  is  very  small  even  when  the  soil  is  extremely 
fertile,  the  bulk  of  the  soil  serving  as  a  support  for  the  plant  and 
as  a  sponge  to  hold  the  water.  Many  chemical  analyses  of  soils 
have  been  made  and  these  show  a  considerable  variation  in  the 
composition  of  soil.  A  good  arable  loam  may  contain  0.15  per 
cent  of  total  nitrogen,  0.15  per  cent  of  total  phosphoric  acid, 
0.10  per  cent  of  total  sulphur  trioxide,  and  0.2  per  cent  of  pot- 
ash and  0.5  per  cent  of  lime,  soluble  in  hydrochloric  acid.  Much 
larger  quantities  may,  of  course,  occasionally  be  present.  Plant 
food  is  not  equally  distributed  throughout  a  soil.  If  a  soil  is 
separated  by  sifting  into  finer  and  coarser  particles,  it  will  be 
found  that  the  finer  particles  are  much  the  richer  in  plant  food. 

The  weight  of  soil  on  an  acre  of  land  is  so  large  that  even 
small  proportions  of  plant  food  may  amount  to  very  consider- 
able quantities.  An  arable  loam  to  the  depth  of  1  foot  will 
weigh,  when  perfectly  dry,  about  4,000,000  pounds.  A  pasture 
soil  will  be  lighter,  the  first  foot  weighing  when  dried  with  the 
roots  removed  about  3,000,000  pounds.  If  such  soils  therefore 


70 


Agricultural  Chemistry 


contain,  when  dry,  0.10  per  cent  of  nitrogen,  phosphoric  acid, 
potash  or  sulphur  trioxide,  the  quantity  of  each  in  1  foot  of 
soil  will  be  from  3,000  to  4,000  pounds  per  acre. 

"When  the  chemist  subjects  the  soil  to  a  chemical  analysis  he 
has  generally  two  things  in  mind, — namely  to  determine  the 
total  plant  food  and  the  "available"  plant  food  in  a  soil.  From 
such  data  he  has  hoped  to  be  able  to  prescribe  just  what  the 
manurial  requirements  of  the  soil  will  be. 

Total  plant  food.  This  method  takes  an  inventory  of  the  soil. 
It  determines  the  total  amount  of  organic  matter,  phosphorus, 
nitrogen,  sulphur,  potassium,  etc.,  irrespective  of  the  combina- 
tions in  which  they  may  exist  in  the  soil.  It  gives  absolute  data 
for  comparison  of  soil  types.  It  takes  an  invoice  of  the  soil's 
supply  of  plant  food  and  such  data  become  of  very  great  value. 
In  the  following  table  are  recorded  some  data  on  the  total  con- 
tent of  plant  food  in  certain  American  soils. 

COMPOSITION  OP  SOME  AMERICAN  SOILS 
Pounds  of  plant  food  per  acre;  depth  62-3  in.,  weight  2,000,000  Ibs. 


Miami 

Galena 

Vicksburg 

Kansas  City 

Dubuque 

silt  loam 

111. 

Miss. 

Missouri 

Iowa 

Madison 

Wisconsin 

PjjOs 

1,400 

2,700 

1,800 

4,500 

3,110 

K20 

41,000 

20,  000 

37,  000 

42,  000 

25,  000 

MgO  

74,  000 

92,000 

22,  000 

22,000 

CaO  

108,  000 

180,000 

34,  000 

32,  000 

Fe20s    .  .  . 

52,000 

50,  000 

75,  000 

70,  000 

S08  

2,000 

2,500 

1,000 

10,000 

2,000 

N  

(3,000 

1,160 

assumed  ) 

J 

The  table  shows  that  most  soils  are  comparatively  low  in  total 
nitrogen,  phosphorus,  and  sulphur  but  generally  contain  large 
reserves  of  potassium,  calcium,  magnesium,  and  iron.  Soils  will 
vary  in  these  respects  and  it  is  generally  true  that  marsh  soils 


TJie  Soil  71 

will  contain  a  large  amount  of  nitrogen  and  a  relatively  small 
quantity  of  potassium.  Sandy  soils  will  also  be  low  in  potas- 
sium as  well  as  phosphorus,  sulphur  and  nitrogen. 

The  total  amount  of  plant  food  present  in  the  soil  is  surpris- 
ing, in  view  of  the  fact  that  it  is  often  difficult  to  maintain  a 
satisfactory  yield  of  crops.  An  acre  of  soil  may  contain  many 
thousand  pounds  of  phosphoric  acid  or  of  nitrogen  and  yet  be  in 
poor  condition;  while  an  application  of  commercial  fertilizer 
supplying  50  pounds  of  readily  available  phosphoric  acid  in  the 
form  of  super-phosphate  or  nitrogen  as  nitrate  of  sodium,  may 
greatly  increase  its  productiveness.  If  we  compare  the  above 
table  with  the  table  in  the  appendix,  showing  the  amount  of 
plant  food  removed  by  various  farm  crops,  it  will  be  seen  that 
the  Galena  111.  soil  shows  the  presence  of  sufficient  nitrogen  for  60 
crops  of  wheat  yielding  30  bushels  per  acre ;  phosphoric  acid  for 
66  crops;  sulphur  trioxide  for  127  crops;  and  potash  enough  to 
supply  1423  such  crops.  There  is,  in  addition,  nearly  as  much 
phosphoric  acid  and  potash  in  the  second  and  third  foot,  so 
that  as  far  as  the  latter  substance  is  concerned,  the  supply  seems, 
almost  inexhaustible.  The  other  two  substances,  nitrogen  and 
phosphoric  acid,  and  probably  a  third,  sulphur,  must  be  con- 
sidered as  limited  in  quantity  in  many  of  our  soils. 

While  chemical  analysis  will  often  disclose  a  large  total  amount 
of  plant  food  sufficient  for  many  crops,  nevertheless  experience 
has  demonstrated  that  long  before  the  theoretical  number  of 
crops  has  been  produced  the  yield  will  have  decreased  so  mate- 
rially as  to  become  unprofitable. 

Available  plant  food.  Total  chemical  analysis  gives  the  ab- 
solute amount  of  nitrogen,  phosphoric  acid  and  potash  in  a  soil, 
but  it  does  not  indicate  what  part  of  these  materials  is  available 
to  the  plant.  It  takes  an  inventory  of  our  stock  on  hand  but 
does  not  measure  the  crop-producing  power  of  the  soil.  A  large 
proportion  of  this  plant  food  is  locked  up  in  insoluble  compounds, 
in  which  form  the  plant  is  unable  to  use  it.  Food  can  be  taken 
up  by  the  roots  of  plants  only  when  in  solution  or  in  a  condition 


72  Agricultural  Cliemistry 

capable  of  being  dissolved  by  contact  with  the  acid  sap  of  the 
root  hairs. 

The  agencies  operative  in  the  soil  and  which  we  have  already 
considered  are  continually  changing  these  insoluble  compounds 
to  forms  available  to  the  plant;  most  of  the  soil  ingredients  are 
in  an  insoluble  form  and  this  fact  is  really  of  the  greatest  im- 
portance, for  if  it  were  not  so  soils  would  then  lose  fertility  by 
heavy  rains.  The  unavailable  or  "potential"  plant  food  is  grad- 
ually being  made  available,  but  not  with  sufficient  rapidity  to 
replace  that  removed  from  the  field  at  harvest,  and  the  yield  of 
crop  produced  will  be  limited  by  the  element  of  this  available 
plant  food  present  in  least  quantity. 

Continuous  cropping  of  the  soil,  with  the  removal  of  everything 
from,  the  field  results  in  the  exhaustion  of  the  plant  food  which 
has  been  rendered  available  during  the  past  ages. 

Potential  or  "reserve"  supply  of  plant  food  is  an  expression 
covering  an  attempt  to  determine  the  amount  of  food  in  a  given 
soil  that  may  become  available  to  plants  over  a  long  period  of 
time.  To  measure  this  capacity  of  the  soil,  an  attempt  is  made 
to  simulate  the  action  of  the  most  vigorous  weathering  agencies. 
For  this  purpose  strong  reagents  must  be  employed.  Concen- 
trated mineral  acids  heated  under  pressure  may  dissolve  silica 
and  its  complexes.  The  same  result  may  be  secured  by  the  use 
of  hydrofluoric  acid  or  the  fusion  of  the  soil  with  alkalies  or  alka- 
line earths  and  subsequent  solution  in  acids.  These  reagents 
proceed  further,  however,  than  do  the  natural  agencies  within 
reasonable  limits  of  time.  Finding  that  a  solution  of  hydro- 
chloric acid  attained  and  maintained  under  distillation  a  density 
of  1.115  (nearly  23  per  cent  strength),  Owen  was  led  to  use  it 
as  an  easily  controlled  reagent  in  soil  analysis;  and  his  method 
has  been  adopted  for  soil  analysis  by  the  official  agricultural 
chemists.  This  reagent  effects  only  partial  decomposition  of  the 
soil  minerals,  giving  only  a  small  proportion  of  the  total  potas- 
sium, calcium,  or  magnesium  present,  but  may  give  all  of  the 


The  Soil  73 

phosphorus.  It  has  very  little  value  in  giving  useful  data  for 
the  soil's  treatment. 

Temporary  supply  of  plant  food  is  a  measurement  of  the 
amount  of  plant  food  in  soils  supposedly  of  immediate  availability 
to  plants.  It  is  the  expression  of  results  obtained  in  an  attempt  to 
duplicate  the  action  of  natural  agents  (such  as  root  acidity, 
bacterial  flora,  plant  decay,  etc.)  on  the  soil.  Various  weak 
solvents  including  water,  carbonated  water,  carbonated  water 
and  ammonium  chloride,  and  dilute  acetic  acid  have  been  used 
for  the  purpose.  Solutions  of  ammonia,  citric  acid,  and  am- 
monium oxalate,  1  per  cent  solution  of  aspartic  acid  and  so- 
lutions of  mineral  acids  were  used.  N/200HC1,  N/5HC1  and 
N/5HNO3  have  been  used  also  for  extracting  the  soil.  In  1894 
Dyer  of  England,  after  extensive  study  of  the  acidity  of  plant 
root  sap,  recommended  a  1  per  cent  solution  of  citric  acid  as 
an  approximation  to  the  natural  solvent  agent  in  plant  feeding. 
Of  all  methods  proposed,  this  appears  to  be  most  substantiated 
by  field  tests,  although  it  is  not  always  by  any  means  a  safe 
guide  to  manurial  requirements.  An  analysis  of  the  extracts 
obtained  with  these  various  solvents  has  been  considered  an  in- 
dex to  the  store  of  ready  available  plant  food  in  the  soil.  None 
of  these  methods  are  general  and  universal  guides  to  the  manurial 
requirements  of  a  soil. 

The  reason  for  this  failure  lies  in  the  complexity  of  factors 
influencing  plant  growth,  among  which  should  be  mentioned  the 
physical  condition  of  the  soil,  the  water  supply  to  the  plant,  the 
biological  agents  operative  in  the  root  zone,  and  the  kind  of 
organic  matter  also  present  in  this  zone.  The  work  of  the  Bureau 
of  Soils,  United  States  Department  of  Agriculture  is  clearly 
showing  that  the  nature  of  the  organic  matter,  which  in  some  in- 
stances may  be  toxic  in  character,  is  a  factor  to  be  reckoned  with 
in  maintaining  the  optimum  environment  for  the  plant 's  develop- 
ment. These  toxic  substances  appear  to  be  produced  in  the  decom- 
position of  the  organic  matter  of  the  soil.  The  munurial  require- 
ments of  a  soil  can  be  definitely  determined  only  by  field  experi- 
ments. (See  page  179.) 


CHAPTER  IV 
NATURAL  WATERS 

Pure  water — or  the  substance  made  of  the  two  elements  hydro- 
gen and  oxygen — practically  never  occurs  in  Nature.  Because 
of  its  great  solvent  properties,  water  always  dissolves  certain 
quantities  of  every  substance  with  which  it  comes  in  contact. 

The  purest  form  of  natural  water  is  rain ;  however,  rain  water 
is  never  pure,  but  contains  varying  quantities  of  dissolved  matter. 
The  quantity  of  dissolved  substances  will  depend  upon  the  lo- 
cality in  which  the  rain  fell.  In  cities  and  in  the  neighborhood 
of  factories  this  will  be  larger  than  in  the  open  country.  The 
character  of  the  substances  in  solution  will  also  depend  upon  the 
locality.  The  rain  water  in  cities,  besides  containing  compounds 
of  nitrogen,  as  ammonium  nitrate,  may  be  acid.  This  is  due  to 
dissolved  sulphuric  acid,  which  had  its  origin  in  the  sulphur  di- 
oxide produced  from  burning  coal.  In  addition  to  these  sub- 
stances rain  water  contains  dissolved  gases. 

When  it  reaches  the  earth  the  water  at  once  begins  to  dissolve 
the  substances  upon  which  it  falls.  In  regions  where  the  surface 
is  composed  of  hard,  igneous  rocks,  the  quantity  of  material  dis- 
solved is  small,  while  on  lime-stone  soils  the  amount  of  calcium 
carbonate  that  goes  into  solution  is  large. 

The  water  which  drains  aAvay  from  a  soil,  partly  finds  its  way 
into  the  nearest  creek,  then  to  a  stream  or  river,  and  finally  to 
the  sea.  Another  portion  sinks  into  the  earth,  until  stopped  by 
some  impervious  layer  of  rock — as  shale  or  hard  pan — wrhen  it 
accumulates  and  eventually  finds  an  outlet  at  some  lower  level  in 
the  form  of  a  spring. 


Natural  Waters  75 

The  industrially  important  waters  may  be  classed  as  follows: 

1.  Rain  water. 

2.  Ground  waters  furnished  by 

(a)  Springs, 

(b)  Shallow  wells  (penetrating  but  one  geological  stra- 

tum), 

(c)  Deep  .wells   (passing  through  more  than  one  such 
stratum) . 

3.  Surface  waters  consisting  of 

(a)  Flowing  waters   (streams). 

(b)  Still  water  (ponds,  lakes,  etc.) 

4.  Sea  water. 

Rain  water.  The  composition  and  character  of  this  has  al- 
ready been  described  in  Chapter  II.  It  contains  very  little  min- 
eral matter  and  is  described  as  "soft"  for  this  very  reason.  If 
it  could  be  collected  without  further  contamination  it  would  be  by 
far  the  best  for  most  purposes.  The  acidity  of  the  rain  in  dis- 
tricts where  much  coal  is  burned  is  of  great  importance  as  af- 
fecting the  growth  of  plants,  particularly  grasses  and  certain 
trees.  In  addition  to  its  direct  injurious  effect  upon  the  foliage, 
it  exerts  a  deleterious  action  upon  the  soil,  tending  to  remove  the 
calcium  carbonate  or  other  basic  material  and  to  promote  "sour- 
ness," a  condition  which  is  very  unfavorable  to  the  growth  of 
most  useful  plants.  It  is  known  that  grass  lands  under  such 
circumstances  become  almost  sterile,  the  last  plants  to  succumb 
to  the  unfavorable  conditions  being  usually  the  "sorrel"  or 
"sweet  dock." 

Ground  water.  The  water  issuing  from  springs  varies  greatly 
in  the  amount  and  nature  of  the  dissolved  matter  which  it  con- 
tains. If  this  be  small,  and  not  possessed  of _  strong  odor  or  taste, 
the  water  is  described  as  fresh  water ;  but  if  a  large  quantity  of 
dissolved  matter  be  present,  or  if  the  water  possesses  pronounced 
taste,  odor,  or  medicinal  properties,  it  is  known  as  a  mineral 
water. 


76  Agricultural  Chemistry 

Many  spring  waters  contain  the  following  substances,  but  in 
varying  amounts: 

1.  Calcium  and  magnesium  carbonates  dissolved  in  excess  of 
carbon  dioxide. 

2.  Calcium  or  magnesium  sulphate. 

3.  Sodium  or  potassium  chloride. 

4.  Alkaline  silicates. 

5.  Dissolved  gases  as  oxygen,  nitrogen  and  especially  carbon 
dioxide. 

Calcium  and  magnesium  carbonates  are  almost  insoluble  in 
water,  but  if  the  water  contains  carbon  dioxide,  the  readily  sol- 
uble bi-carbonates  of  calcium  and  magnesium  are  formed. 

Such  action  occurs  in  all  lime-stone  districts  and  the  removal 
of  the  rock  by  solution  gives  rise  to  the  caves  and  underground 
water  courses  so  common  in  such  localities.  The  great  Mammoth 
Cave  of  Kentucky  and  Perry  Cave  of  Northern  Ohio  are  illus- 
trations of  such  action. 

When  such  water  is  boiled  the  bi-carbonates  are  decomposed, 
losing  part  of  their  carbon  dioxide,  and  normal  carbonates  are 
again  formed.  These  are  insoluble  and  consequently  appear  as 
a  precipitate.  In  many  cases  the  precipitated  calcium  or  mag- 
nesium carbonate  forms  a  firmly  adherent  coating  or  crust  upon 
the  bottom  or  sides  of  the  kettle  or  boiler. 

Calcium  and  magnesium  sulphates  are  soluble  in  water,  the 
former  to  the  extent  of  about  1.7  grams  per  liter  (1  oz.  in  18 
quarts  of  water).  Waters  containing  calcium  or  magnesium 
compounds  are  known  as  "hard"  waters,  and  have  a  peculiar 
and  well  known  action  on  soap.  The  latter  is  essentially  a  sodium 
salt  of  the  fatty  acids,  as  stearic,  palmitic  and  oleic  acids.  These 
acids  are  the  constituents  of  our  principal  fats  and  it  is  the  com- 
mon practice  of  every  good  housewife  to  save  the  fat  "scraps" 
for  the  home  soap-making.  The  sodium  and  potassium  salts  of 
the  fatty  acids  are  soluble  in  water,  but  the  calcium  and  mag- 
nesium salts  are  insoluble.  For  water  to  form  a  lather  with 
soap  or  properly  exercise  its  cleansing  power,  it  is  necessary  that 


Natural  Waters  77 

the  water  should  contain  in  solution  some  of  the  sodium  or  potas- 
sium salts  of  the  fatty  acids.  When  a  small  quantity  of  soap  is 
dissolved  in  hard  water,  the  calcium  or  magnesium  present  in 
the  water  displaces  the  sodium  or  potassium  and  gives  a  curdy, 
flocculent  precipitate  of  the  calcium  or  magnesium  salts  of  the 
fatty  acids.  The  dissolved  soap  is  thus  removed  and  more  has 
to  be  dissolved  before  the  proper  cleansing  action  can  be  exerted. 
Hence  hard  waters  are  unsuitable  for  domestic,  especially  for 
laundry,  purposes;  they  involve  the  consumption  of  large  quan- 
tities of  soap  and  contaminate  the  washed  articles  with  the  pre- 
cipitated "lime"  or  "magnesia  soap." 

Hard  waters  are  also  unsuitable  for  steam-raising,  since  the 
deposit  of  calcium  carbonate  or  calcium  sulphate  (boiler  scale) 
upon  the  boiler  plates  greatly  increases  the  consumption  of  fuel 
required  for  the  production  of  a  certain  quantity  of  steam.  Cal- 
cium carbonate  alone  forms  a  porous  and  non-adherent  scale, 
which  is  easily •  removed  by  "blowing  off"  the  boiler.  Calcium 
sulphate  forms  a  hard  compact  scale,  which  adheres  very  firmly. 

A  distinction  is  often  made  between  waters,  which  contain 
their  calcium  and  magnesium  as  bi-carbonates  and  those  in  which 
the  salts  present  are  as  sulphates.  The  former  are  known  as 
"temporarily"  the  latter  as  "permanently"  hard  waters.  By 
the  removal  of  the  excess  of  carbon  dioxide  from  the  former  the 
calcium  and  magnesium  carbonates  are  precipitated,  while  with 
the  latter  the  salts  are  in  solution  and  cannot  be  precipitated  by 
the  simple  removal  of  carbon  dioxide. 

The  usual  method  of  procedure  to  effect  the  softening  of  tem- 
porarily hard  water  is  to  add  "milk  of  lime"  in  sufficient  quan- 
tity to  combine  with  the  free  carbon  dioxide  and  that  present  as 
bi-carboiiates.  The  precipitate  formed  will  be  found  to  contain 
the  calcium  and  magnesium  carbonates  originally  present,  to- 
gether with  that  formed  from  the  added  lime.  On  standing,  the 
precipitate  settles  out  and  the  clear  liquid  is  then  almost  free 
from  calcium  and  magnesium  and  is  "soft."  The  milk  of  lime 
should  be  added  slowly  and  gradually  and  care  be  taken  that  no 


78  Agricultural  Chemistry 

great  excess  is  used.  Water  so  treated  is  much  improved  both 
for  washing  and  for  steam-raising  purposes.  The  "milk  of 
lime"  is  made  by  treating  a  quantity  of  quick  lime  with  water 
and  after  thoroughly  stirring,  the  "milk"  is  then  mixed  with  the 
water  to  be  purified. 

Another  method  is  to  boil  the  water  either  in  the  open  air  or 
in  special  heaters.  This  decomposes  the  bi-carbonates,  drives  out 
the  excess  of  carbon  dioxide  and  the  normal  carbonates  of 
magnesium  and  calcium  settle  out  as  precipitates. 

Permanent  hardness  is  less  easily  remedied,  for  in  every  case 
the  treatment  of  the  water  leaves  in  solution  some  substance  more 
or  less  deleterious.  Sodium  carbonate  and  barium  chloride  are 
the  materials  in  common  use.  A  recent  suggestion  calls  for  the 
use  of  sodium  bi-chromate  within  the  boiler,  as  a  corrective  for 
both  temporary  and  permanent  hardness.  It  is  claimed  that  the 
calcium  and  magnesium  chromates  precipitate  in  the  boiler  as  a 
loose,  non-adherent  mass,  which  is  removed  by  "blowing  off" 
daily.  It  is  further  claimed  that  the  free  chromic  acid  does  not 
attack  the  boiler  iron.  Much  care  is  necessary  in  order  to  avoid 
an  excess  of  any  chemical  added.  As  a  rule  the  water  should  be 
treated  before  it  goes  into  the  boiler.  But  if  the  scale-forming 
material  does  not  exceed  150  parts  per  million,  the  purification 
may  be  done  in  the  boiler  itself,  followed  by  daily  "blowing  off." 

A  great  many  proprietary  "anti-scale"  preparations  are  sold, 
many  of  which  are  of  no  particular  value.  Most  of  them  are  to 
be  used  inside  the  boilers.  Some  are  supposed  to  act  chemically 
on  the  impurities  and  others  are  mechanical,  preventing  the  ad- 
herence of  scale.  The  former  usually  contain  soda-ash,  caustic 
soda,  barium  hydroxide,  or  sodium  phosphate.  Tannin  in  the 
form  of  sodium  tannate,  is  sometimes  employed,  by  which  the 
calcium  and  magnesium  are  separated  as  tannates.  Graphite  is 
an  example  of  the  mechanical  "anti-scale"  preparations. 

In  a  drinking  water  the  presence  of  calcium  compounds,  except 
perhaps  in  excessive  amounts,  is  not  objectionable.  Indeed,  it  is 
often  advantageous,  furnishing  a  portion  of  the  lime  necessary 


Natural  Waters  ,;iy  79, 

for  the  building  up  of  the  hard  parts,  such  as  bones  or  shells,  of 
the  animal.  Moreover,  in  many  cases  water  is  delivered  through 
lead  pipes  and  soft  waters,  especially  if  they  contain  vegetable 
acids,  as  for  example  peaty  waters,  attack  and  dissolve  the  lead, 
and  often  to  such  an  extent  as  to  cause  lead  poisoning  in  those 
who  drink  them.  The  presence  of  calcium  sulphate  renders  wa- 
ter incapable  of  this  dangerous  action  upon  the  lead.  In  the 
presence  of  calcium  sulphate  the  metal  becomes  coated  with  a 
film  of  the  very  insoluble  lead  sulphate,  which  protects  it  from 
further  contact  with  the  water. 

Organic  matter.  Of  greater  importance  than  the  mineral  mat- 
ter in  drinking  water,  is  the  amount  and  nature  of  the  organic 
matter.  This  in  itself  is  comparatively  harmless.  Its  import- 
ance lies  in  the  influence  it  may  have  upon  the  kinds  of  micro- 
organisms which  accompany  it.  Animal  excreta  is  the  most  dan- 
gerous contamination,  since  the  micro-organisms  which  cause 
various  diseases,  as  for  example,  typhoid,  cholera,  etc.,  are  liable 
to  be  thus  introduced  into  the  water.  Animal  organic  matter  is 
richer  in  nitrogen  than  most  vegetable  refuse,  so  that  in  practice 
the  detection  of  much  combined  nitrogen,  whether  as  organic 
matter,  ammonium  salts,  or  nitrates,  is  regarded  as  sufficient  to 
indicate  that  the  water  has  been  contaminated  with  sewage  or 
other  animal  matter.  If  much  organic  matter  of  animal  origin 
be  present  there  must  always  be  considerable  risk  of  disease  pro- 
ducing organisms  finding  their  way  into  the  bodies  of  those  who 
drink  it ;  and  though  such  contaminated  water  may  be,  and  often 
is,  drunk  for  years  with  impunity,  its  consumption  is  decidedly 
dangerous. 

Another  substance  characteristic  of  sewage  is  common  salt; 
consequently  the  presence  of  much  chlorine  in  a  water  is  gen- 
erally indicative  of  sewage  contamination,  unless  the  water  is 
derived  from  some  rock  which  contains  salt,  or  is  collected  near 
the  sea. 

What  has  been  said  has  an  important  bearing  upon  the  loca- 
tion of  the  farm  wells.  Dangers  of  seepage  from  the  out  door 


80 


Agricultural  Chemistry 


privy  and  the  barn-yard  must  be  avoided  by  locating  the  well 
at  a  proper  distance  from  both  and  on  higher  ground.  Even 
these  precautions  may  not  always  entirely  remove  the  danger  of 
contamination. 

Analyses,  quoted  from  Ingle,  of  typically  good  and  bad  drink- 
ing waters,  are  given  below. 

Composition  of  Good  and  Bad  Drinking  Waters. 


Constituents 

Good  water 
Parts  per  million 

Bad  water 
Parts  per  million 

Total  solids  

63 

530 

Nitrogen  as  nitrites  and  nitrates  
Free  ammonia  

0.25 
0.03 

7.8 
4.3 

Albuminoid  ammonia  

0.07 

0.9 

Chlorine  

11.4 

69 

Tern,  hardness   

1.4 

102.9 

Per.  hardness  

34.3 

205.9 

Total  hardness  

35.7 

308.8 

By  hardness  is  meant  the  parts  of  calcium  carbonate  equiva- 
lent to  the  total  amount  of  calcium  and  magnesium  salts  present 
in  one  million  parts  of  the  water. 

By  albuminoid  ammonia  in  the  above  table  is  meant  the  quan- 
tity of  ammonia,  which  is  evolved  from  the  water  by  the  decom- 
position of  organic  nitrogenous  substances  when  distilled  with  an 
alkaline  solution  of  potassium  permanganate. 

Surface  water.  Rivers,  ponds  and  lakes  belong  to  this  class. 
Most  rivers  originate  in  springs,  so  at  first  their  water  resembles 
that  of  their  source.  A  considerable  influx  of  surface  water, 
however,  generally  enters  the  river  and  alters  its  composition. 
The  composition  of  the  waters  of  ponds  or  lakes  will  be  much  like 
that  of  the  creeks  and  rivers  flowing  into  them.  The  surface 
water  usually  contains  less  dissolved  matter  than  spring  water, 
but  often  more  organic  matter  and  suspended  particles.  The 
composition  of  the  river  water  depends  greatly  upon  the  char- 


Natural  Waters 


81 


acter  of  the  rocks  from  which  it  is  collected.  When  the  surface 
consists  of  igneous  rocks  or  of  sandstone,  the  water  is  usually 
soft,  while  in  lime  stone  districts  it  will  be  hard.  Some  rivers, 
as  for  example  the  Trent  of  England,  are  rich  in  calcium  sul- 
phate arid  to  this  fact  the  excellence  of  the  Burton  ales  has  been 
ascribed.  The  remarkable  softness  of  the  river  Dee,  which  flows 
through  the  granite  district  of  Aberdeenshire,  England,  is  also 
worthy  of  special  notice. 

The  following  table  represents  the  average  composition  of  sev- 
eral well  known  lake  waters  of  Wisconsin . 


Composition  of  Wisconsin  Lake  Waters. 


Parts  per  Million 


Lake  Mendota 

North  Lake 

Devil's  Lake 

Silica  

1.1 

3.0 

2.2 

Alumina  and  iron  

0.8     . 

0.6 

0.6 

Lime  

40.1 

66.2 

4.5 

Magnesia  

42.3 

46.4 

1.8 

10.3 

11.1 

6.7 

Chlorine  

2.0 

4.0 

8.2 

The  softness  of  the  water  of  Devil's  lake  is  also  to  be  attributed 
to  the  fact  that  it  is  located  in  a  sandstone  country. 

River  water  rarely  contains  large  quantities  of  calcium  carbon- 
ate such  as  occur  in  some  springs,  since,  owing  to  the  free  con- 
tact with  air  it  never  retains  very  large  quantities  of  dissolved 
carbon  dioxide.  Calcium  sulphate  in  river  water  is  usually  ac- 
companied by  sodium  chloride  and  magnesium  salts. 

In  thickly  populated  and  manufacturing  centers  the  rivers  are 
contaminated  with  the  sewage  and  trade  effluent  of  the  towns 
and  villages,  and  thus  often  become  foul  and  bad-smelling.  This 
is  to  be  deplored  both  on  account  of  the  annoyance  and  injury 
to  health  which  they  cause,  and  also  because  of  the  serious  loss 


82  Agricultural  Chemistry 

to  the  community  of  the  valuable  combined  nitrogen  and  other 
manurial  constituents  contained  in  the  sewage.  It  is  estimated 
that  the  Mississippi  river  carries  daily  to  the  sea  50  to  100  tons 
of  nitrogen  as  nitrates.  In  some  cities  of  America,  as  well  as  in 
Europe,  the  sewage  is  pumped  directly  to  nearby  lands  called 
"sewage  farms,"  where  it  is  allowed  to  run  at  intervals  between 
thrown-np  earth  ridges.  On  these  ridges  various  crops,  especially 
vegetables,  are  grown,  with  the  resultant  utilization  of  the 
manurial  constituents  of  the  sewage. 

The  amount  of  suspended  matter  in  river  water  varies  enor- 
mously, depending  upon  the  rain  fall,  the  character  of  the  sur- 
rounding soil,  and  other  circumstances.  Soft  waters  or  those  con- 
taining carbonate  of  soda,  are  often  muddy,  while  hard  waters 
tend  to  deposit  their  suspended  clay  and  become  clear.  In  some 
cases  the  quantity  of  suspended  matter  is  very  great,  and  a  dense 
muddy  river,  if  it  over-flows  its  banks,  deposits  upon  the  soil 
a  layer  of  finely  divided  particles  of  materials  brought  down 
from  higher  up  the  valley.  The  sediment  is  often  rich  in  plant 
food  and  forms  an  important  fertilizer.  In  some  places  in  Eng- 
land, land  is  systematically  treated  with  the  flood  water  in  order 
to  increase  the  thickness  of  the  soil.  The  process  is  known  as 
"warping"  and  the  "warp"  soils  are  extremely  rich  and  fertile. 
The  Nile  river  in  Egypt  affords,  on  a  large  scale,  a  still  better 
example  of  a  river  used  in  this  manner. 

In  countries  of  limited  or  unevenly  distributed  rainfall,  as  in 
many  of  our  western  states,  irrigation  is  often  practiced.  In 
this  case,  since  there  is  very  little  drainage,  the  composition  of 
the  water  used  is  of  importance.  If  the  water  is  charged  with 
common  salt,  sodium  sulphate  or  sodium  carbonate,  there  is  grave 
danger  of  the  surface  soil,  through  the  prolonged  evaporation 
and  concentration  of  the  water,  becoming  charged  with  the  sol- 
uble matter  to  such  an  extent  as  to  seriously  interfere  with  plant 
growth.  The  soil  is  then  said  to  become  "alkali."  This  con- 
dition may  also  arise  from  accumulation-in-place  of  the  salts, 
produced  by  the  weathering  of  the  rocks.  The  slight  rain  fall  is 


Natural  Waters 


83 


insufficient  to  produce  percolation  through  the  soil  and  carry 
the  accumulating  salts  into  the  under  ground  water  system.  This 
produces  a  sterile  condition  which  may  be  caused  by  sodium  sul- 
phate and  chloride  (white  alkali),  or  by  sodium  carbonate  (black 
alkali). 

Different  crops  are  possessed  of  different  resisting  powers  to 
these  salts.  As  a  rule  sodium  carbonate  is  the  most  effective  in 
causing  injury  to  plants  and  sodium  sulphate  the  least.  For- 
tunately, however,  "black  alkali" — i.  e.,  sodium  carbonate — can 
be  rendered  almost  harmless  by  the  application  of  gypsum  to  the 
soil,  which  decomposes  the  sodium  carbonate  with  formation  of 
the  very  much  less  harmful  substances,  sodium  sulphate  and 
calcium  carbonate.  If  "white  alkali"  is  due  to  common  salt,  it 
cannot  be  cured  except  by  drainage. 

According  to  results  accumulated  in  this  country,  and  tabu- 
lated by  Ingle,  the  following  figures  give  the  highest  proportion 
of  sodium  chloride,  sodium  sulphate  and  sodium  carbonate  wrhich 
may  be  present  in  soils  without  injury  to  the  plants  named.  The 


Plant 

Sodium 
Chloride 

Sodium 
Sulphate 

Sodium 
Carbonate 

Grape  

9,640 

40,800 

7,  550 

Fig.. 

800 

24,  480 

1,120 

Orange  

3,360 

18,000 

3,840 

ADnle  .  . 

1,240 

14,  240 

640 

Peach  

1,000 

9,600 

680 

Oriental  Sycamore  

20,  320 

19,  240 

3,200 

Salt  bush        

12,  520 

125,  640 

18,  560 

Alfalfa,  old  

5.760 

102,  4HO 

2,360 

Sugar  beet  

ft,  440 

52,640 

4,000 

Radish    

2,240 

51,880 

8,720 

Wheat  

1,160 

15,  120 

1,480 

Barley     

5,100 

12,  020 

12,  170 

Sorghum  

9,680 

61,840 

9,840 

figures  represent  the  amounts  in  pounds  of  the  various  constit- 
uents present  in  the  upper  four  feet  of  soil  per  acre : 

In  this  table  it  is  assumed  that  the  weight  of  soil  to  a  depth 


84  Agricultural  Chemistry 

of  four  feet  per  acre  is  16,000,000  pounds,  or  that  each  acre-foot 
of  soil  weighs  4,000,000  pounds.  One  per  cent  of  any  constituent 
would  then  correspond  to  40,000  pounds  per  acre  to  a  depth  of 
one  foot,  one-tenth  per  cent  to  4,000  pounds,  and  so  on. 

Sea  water  varies  in  composition,  dependent  upon  the  locality 
at  which  it  is  taken.  Its  composition  is  affected  by  the  influx 
of  fresh  water  from  large  rivers,  etc.,  but  far  out  from  land  it 
is  very  constant  in  composition.  The  average  amount  of  total 
solid  matter  is  about  34,000  parts  per  million.  Thorpe,  in  1870, 
found  in  the  water  of  the  Irish  sea  the  following  constituents 
expressed  in  parts  per  million: 

Sodium  chloride    26,439    I   Magnesium  nitrate 2 

Potassium  chloride  746      Calcium  sulphate   1,332 

Magnesium  chloride 3,150 

Magnesium  bromide 71 

Magnesium  sulphate    2,066 


Calcium  carbonate 48 

Ammonium  chloride  ....  0.4 

Ferrous  carbonate 5 


Magnesium  carbonate Trace      Silicic    acid    Trace 

In  certain  lakes  having  no  connection  with  the  ocean,  the  con- 
centration of  the  water  becomes  much  greater,  and  the  total  solid 
matter  may  reach  even  seven  or  eight  times  that  found  in  the 
ocean.  Examples  of  such  water  are  found  in  the  Dead  Sea  and 
the  Great  Salt  Lake  of  Utah. 


CHAPTER  V 

THE  PLANT 

The  growth  of  plants  is  the  result  of  a  series  of  chemical  and 
physical  changes  which  first  assume  prominence  in  the  sprouting 
seed,  with  the  ultimate  object  of  producing  seed  for  a  succeeding 
generation.  The  effects  of  these  changes  become  inconspicuous  in 
resting  seeds,  but  their  activity  ceases  only  with  the  death  of  the 
organism. 

Germination.  A  seed  is  essentially  an  embryonic  plant  sur- 
rounded and  protected  by  a  supply  of  reserve  materials  which 
serve  as  food  until  the  young  plant  can  forage  for  itself.  These 
reserve  compounds  are  more  or  less  complex  structures  involving 
simple  plant-food  constituents  derived  from  the  air  and  soil. 
The  changes  by  which  they  are  altered  for  the  use  of  the  seedling 
are  produced  by  sensitive  compounds  known  as  enzymes. 

These  compounds  are  not  endowed  with  life,  but  they  are 
probably  closely  related  in  composition  to  the  complex,  nitro- 
genous compounds  known  as  proteins,  which  form  the  basis 
of  living  matter,  and  with  whose  chemical  changes  the  life  pro- 
cesses of  plants  and  animals  appear  to  be  very  closely  connected. 
The  exact  nature  of  enzyme  action  is  not  known.  One  of  the 
theories  attributed  their  effects  to  a  sympathetic  relation  where- 
by they  induced  instability,  or  accentuated  conditions  already  un- 
stable, in  certain  other  compounds  and  caused  them  to  break 
down.  This  theory  is  insufficient  for  we  now  know  that  enzymes 
can  effect  the  construction,  as  well  as  the  destruction,  of  some 
compounds.  Under  proper  conditions  of  temperature  and  moist- 
ure small  amounts  of  a  given  enzyme  induce  changes  in  a  large 
amount  of  matter,  each  kind  of  enzyme  acting  upon  a  specific 
compound  or  group  of  compounds.  Thus,  a  specific  type  of  en- 
zymes, designated  as  proteolytic  in  nature,  cleaves  the  protein 
compounds  of  the  germinating  seed  to  simpler  soluble  compounds 
including  the  amino  acids ;  an  enzyme  known  as  diastase  converts 


86  Agricultural  Chemistry 

starch  to  dextrins  and  sugar;  a  lipase  or  fat  splitting  enzyme 
acts  only  upon  fats,  converting  them  to  glycerine  and  fatty  acids. 
These  changes  are  hydrolytic,  that  is,  they  involve  the  combining 
of  the  substance  attacked  with  water.  Another  type  of  enzyme 
liberates  phosphorus,  calcium  and  other  ash  constituents  from  or- 
ganic compounds  of  the  seed.  Phytase,  which  occurs  in  wheat 
and  other  grains,  is  an  example  of  the  last  mentioned  class  of 
enzymes.  It  breaks  up  the  compound  known  as  phytin,  produc- 
ing simple  soluble  compounds  of  calcium,  magnesium,  potassium 
and  phosphorus.  Other  enzymes,  the  oxidases,  cause  the  oxida- 
tion of  various  organic  compounds. 

Consideration  of  this  specific  relation  between  enzymes  and 
organic  compounds  and  extension  of  our  knowledge  concerning 
the  chemical  structure  of  the  substances  involved  therein  have 
led  to  a  theory  which  likens  the  action  of  an  enzyme  to  that 
of  a  key  upon  a  lock,  in  the  sense  that  each  key  fits  and  trips 
only  the  particular  lock  to  which  it  is  adapted.  This  is  more 
complete  than  the  older  theory,  for  it  ascribes  to  the  enzyme 
power  to  reconstruct  its  specific  compound  just  as  the  key  can 
lock  as  well  as  unlock.  It  is  in  harmony  with  the  known  re- 
versibility of  some  enzyme  actions. 

The  new  compounds  resulting  from  enzymatic  action  in  the 
seed,  combining  in  part  with  the  oxygen  of  the  air  always  re- 
quired for  germination,  either  yield  energy  for  the  growth  of  the 
3roung  plant,  or  pass  as  soluble  compounds  with  the  sap  into  the 
growing  seedling,  there  to  be  reconstructed  into  compounds  form- 
ing the  tissues  of  the  young  plant. 

By  the  time  the  reserve  compounds  of  the  seed  are  exhausted 
the  young  plant  is  differentiated  into  separate  organs,  known  as 
root,  stem  and  leaf,  by  means  of  which  it  can  assimilate  raw  food 
materials  from  the  air  and  soil. 

Functions  of  the  root.  The  root  is  an  organ  of  great  import- 
ance in  the  assimilation  of  food.  Large  amounts  of  water  re- 
quired by  the  growing  plant,  are  taken  from  the  soil  by  means 
of  the  root  and  it  is  through  this  means  that  the  plant  obtains 
its  nitrogen  and  ash  constituents. 


The  Plant 


87 


The  activity  of  this  organ  in  this  connection  is  shown  by  the 
following  figures  quoted  from  King.  The  table  expresses  the 
pounds  of  water  required  to  produce  1  pound  of  dry  substance 
in  the  plant. 

Pounds  of  Water  Required  to  Produce  One  Pound  of  Dry  Substance. 
Kind  of  Plant  Pounds  of  Water 

Dent  Corn 309.8 

Barley    392.9 

Oats 522.4 

Red  Clover  452.8 

Field   Peas 477.4 

Potatoes 422.7 

"When  we  consider  that  field  crops  require  an  amount  of  water 
from  three  hundred  to  five  hundred  times  as  great  as  their  own 
dry  weight,  and  that  all  of  their  nitrogen  (except  in  the  case  of 


Showing  the  power  of  the  rutabaga  to  obtain  its  phosphorus  from  insol- 
uble phosphates. 

Box  1.     Soluble  phosphoric   acid. 
Box  2.     Insoluble  phosphoric  acid — Florida  rock 
Box  3.     Insoluble  phosphates  of  iron  and  aluminum. 
Box  4.     No  phosphate  added. 

leguminous  plants)  and  all  of  their  ash  constituents  are  derived 
from  the  soil  with  this  supply  of  water,  the  great  importance  of 
the  function  of  assimilation  performed  by  the  roots  becomes  evi- 
dent. 


88 


Agricultural  Chemistry 


While  some  plants,  as  for  example,  tobacco  and  the  potato,  re- 
quire liberal  supplies  of  plant  food  in  readily  available  form, 
others,  especially  the  cruciferae  (turnip,  rutabaga  and  related 
plants)  and  some  of  the  gramineae  (cereal  grains  and  grasses), 
display  marked  ability  to  attack  resistant  compounds  in  the  soil 
and  obtain  food  from  them.  This  difference  is  well  illustrated  by 
the  following  data  obtained  by  Merrill  at  the  Maine  Experiment 
Station  in  studying  the  availability  of  phosphorus,  when  sup- 
plied in  various  forms  to  different  crops.  Other  requirements 
of  the  plants  than  that  for  phosphorus  were  amply  supplied. 
The  figures  express  the  percentage  yield  of  dry  matter,  the  yield 
with  no  phosphorus  being  taken  as  100  per  cent : 


Phos- 

Phos- 

Phos- 

No 

phorus 

phorus 

phorus 

Plant  Family 

Crop 

Phos- 

in ground 

in  iron  and 

in  water 

phorus 

Florida 

aluminum 

soluble 

rock 

phosphate 

forms 

Per  cent 

Per  cent 

Per  cent 

Per  cent 

Leguminosae  

100 

140.4 

108  6 

191  8 

Clover  

100 

205  1 

152  4 

262  2 

Barley  

100 

117.7 

128.1 

232.5 

100 

273.6 

316.6 

704.2 

Potato  

100 

114.1 

121.6 

161  2 

Tomato  

100 

255.7 

218.8 

376.1 

Cruciferae  

Turnip  

100 

159.0 

204.2 

226.6 

Rutabaga  .  .  . 

100 

286.0 

216.6 

378.1 

These  data  show  a  widely  variant  power  on  the  part  of  plants 
to  assimilate  comparatively  insoluble  and  unavailable  compounds 
of  phosphorus.  The  great  superiority  of  corn  over  barley  and 
of  the  tomato  over  the  potato  in  utilizing  the  insoluble  phos- 
phates is  interesting  as  a  demonstration  that  assimilating  power 
is  not  uniform  for  members  of  a  plant  family,  but  is  a  charac- 
teristic of  the  individual  species.  The  cruciferae,  however,  as  a 
family,  are  notably  efficient  as  phosphorus  gatherers,  while  the 
grass  family  is  characterized  by  high  assimilation  of  silicon. 


The  Plant  89 

The  well  known  power  of  roots  to  etch  the  surface  of  lime- 
stone is  due  to  excretion  of  carbon  dioxide  from  this  organ  of  the 
plant,  and  differences  in  ability  to  assimilate  food  materials  may 
be  explained  partly  by  differences  in  carbon  dioxide  output. 

If  the  stem  of  an  actively  growing  plant  be  severed  at  its  junc- 
tion with  the  root  and  replaced  by  a  pressure  gauge,  it  will  be 
found  that  the  root  exerts  an  upward  pressure  amounting  in 
some  cases  to  more  than  30  pounds  per  square  inch.  According 
to  Wider  this  pressure  has  been  found  sufficient  to  support  a 
column  of  water  of  the  following  heights  in  the  plants  indicated : 

Height  of  water  column 
Plant  supported  by  root  pressure 

White  Mulberry  6.5  inches 

European  Ash 11.4       " 

Castor    Oil    Plant    181.3      " 

Stinging  Nettle  249.7       " 

Wine  Grape  581.6      " 

White  Birch    755.0      " 

Sweet  Birch  (Black  Birch)   1043.2      " 

By  this  so-called  "root  pressure"  the  root  is  believed  to  func- 
tion in  the  movement  of  water  through  the  plant. 

In  biennial  root  crops  such  as  the  beet,  the  root  of  the  first 
year's  growth  serves  as  a  magazine  for  food  from  which  the 
second  year's  growth  is  re-inforced  for  the  production  of  seed. 
This  reinforcing  material  is  usually  starch  or  sugar,  with  small 
amounts  of  nitrogen  compounds  and  ash  constituents. 

The  stem.  The  active  portion  of  the  stems  of  plants  consists 
essentially  of  a  system  of  tubes  combined  in  groups  known  as 
conducting  bundles.  These  tubes  serve  as  channels  for  the  trans- 
portation of  water  and  food  materials  and  are  .surrounded  by 
protecting  and  supporting  tissue.  In  the  stems  of  endogenous 
plants,  as  in  the  corn  and  the  bamboo,  the  tough,  smooth  bark 
is  formed  by  aggregates  of  the  dead  remains  of  conducting  bun- 
dles and  newer  growths  are  added  by  increments  of  these  bun- 
dles in  the  soft  pith  toward  the  center  of  the  stem.  Groups  of 


90  Agricultural  Chemistry 

these  cells,  which  traverse  the  pith  of  the  stalk  longitudinally, 
are  familiarly  known  as  the  fiber  of  hemp  and  the  threads  of 
the  corn  stalk.  The  stems  of  exogenous,  plants  like  the  oak  and 
maple,  which  produce  new  tissue  outward  from  a  compact,  central 
heart-wood,  consist  of  a  tough,  supportive  core  of  the  older  and 
denser  tissue  surrounded  by  the  growing  cambium  layer.  This 
whole  structure  is  surrounded  and  protected  by  a  layer  of  dead 
cells  forming  the  outer  bark.  Sap  is  conveyed  about  these  plants 
through  channels  in  the  cambium  layer  or  inner  bark,  and  may  be 
obtained  in  quantity  from  some  trees,  as  from  the  sugar-maple, 
by  tapping  into  the  inner  bark  and  contiguous  woody  tissue  in 
early  spring,  when  the  rapidly  developing  buds  are  drawing  upon 
reserve  food  supplies  in  the  trunk.  In  the  case  of  the  maple 
tree,  starch  and  other  reserve  carbohydrates  are  in  process  of 
transportation  to  the  buds  in  the  form  of  sugars  which  may  be 
recovered  as  such  by  concentrating  the  sap. 

The  steins  of  some  plants  have  the  appearance  of  roots  from 
the  fact  that  they  exist  below  the  surface  of  the  soil.  The  pods 
of  the  peanut,  for  example,  ripen  in  the  ground  because  the 
flower  stems  lengthen  and  penetrate  the  soil  as  soon  as  the  blos- 
som falls. 

Root  stocks  or  rhizomes  are  subterranean  stems,  each  joint  or 
node  of  which  puts  out  both  leaf  buds  and  roots.  Each  node 
is  thus  equipped  to  become  an  independent  plant  as  soon  as  it  is 
isolated  from  the  parent  stem.  It  is  to  this  fact  that  the  ex- 
treme troublesomeness  of  quack  grass  is  due.  Cultivation,  ex- 
cept in  a  favorable  season  of  prolonged  drought,  serves  to  in- 
crease the  pest.  Asparagus  is  another  example  of  a  plant  grow- 
ing from  a  rhizome  and  well  illustrates  the  function  of  the  stem 
as  a  food  magftzine. 

Tubers  are  fleshy  enlargements  of  the  tips  of  subterranean 
stems.  Their  "eyes"  mark  the  position  of  buds,  which  distin- 
guish them  from  true  roots.  Each  of  these  eyes  is  the  precursor 
of  one  or  more  new  plants.  The  tubers  of  the  potato,  arrow 
root,  and  some  other  plants,  are  of  great  value  as  food  because 


The  Plant  91 

of  their  high  starch  content.  In  these  cases  the  stems  serve  as 
storage  places  for  reserves  of  plant  food.  The  bulbs  of  the  onion, 
lily  and  other  plans,  are  permanent  buds,  formed  of  fle'shy, 
closely  packed  scales.  They  are  properly  a  part  of  the  stem  of 
the  plant,  .serving  as  reserve  material  for  growth.  The  fleshy 
portion  of  the  crocus,  gladiolus  and  some  other  plants  is  not  a 
bulb,  but  is  an  enlargement  of  the  base  of  the  stem. 

The  stem  also  serves  as  a  means  of  support  for  the  leaves  and 
fruit,  favoring  the  exposure  of  both  to  the  air  and  sunlight  es- 
sential to  the  chemical  processes  which  promote  growth. 

The  leaf.  The  leaf  is  the  seat  of  greatest  constructive  activ- 
ity in  the  plant.  The  important  process  of  transpiration,  or  es- 
cape of  water  from  the  plant,  is  controlled  by  minute  openings 
upon  the  plant's  surface.  These  openings,  known  as  stomata, 
occur  in  small  numbers  upon  the  stems  of  plants,  but  they  are 
most  abundant  upon  the  leaves.  They  are  especially  numerous 
upon  the  protected  under  surface  of  leaves,  where,  as  in  the  case 
of  the  cabbage  or  apple,  their  number  may  reach  200,000  per 
square  inch.  The  outlet  of  a  stoma  is  lined  by  two  peculiar  cells 
which  face  each  other,  forming  a  miniature  mouth  opening  out- 
ward from  the  surface  of  the  leaf.  These  cells,  called  guard  cells, 
are  the  seat  of  control  in  the  action  of  the  stomata.  When  the 
water  supply  is  abundant  and  the  plant  cells  are  turgid,  the 
guard  cells  are  elongated  vertically  to  the  leaf  surface  and  con- 
tracted parallel  to  it,  thus  drawing  apart  and  exposing  an  outlet 
for  the  evaporation  of  water.  On  the  other  hand,  when  the  wa- 
ter supply  is  limited  and  the  plant  cells  wilt  or  shrink,  the  guard 
cells  flatten  and  become  elongated  parallel  to  the  leaf  surface, 
thus  automatically  closing  the  stomata  and  checking  evaporation 
from  the  plant.  This  process  partly  controls  the  supplying  of 
plant  food  from  the  soil  and  is  an  important  means  of  maintain- 
ing optimum  temperatures  in  the  plant  as  a  result  of  increased 
or  decreased  evaporation  of  water. 

From  the  supply  of  air  which  enters  it  through  the  stomata, 
the  leaf  assimilates  carbon  dioxide  for  the  construction  of  plant 


92  Agricultural  Chemistry 

compounds  and  employs  oxygen  in  the  process  of  respiration  ana- 
logous to  that  of  animals. 

The  magnitude  of  the  former  process  can  be  realized  when  we 
recall  that  a  12  ton  crop  of  corn  requires  for  its  production  four 
tons  of  carbon  dioxide.  To  secure  this  amount,  the  plants  must 
respire  10,000  tons  of  air  or  approximately  one-fourth  of  the 
total  amount  over  an  acre  of  land. 

The  construction  of  organic  compounds,  which  is  a  character- 
istic function  of  the  plant  occurs  principally  in  the  leaf.  It  is 
initiated  by  the  green  coloring  matter  known  as  chlorophyll, 
C55H7206N4Mg.  This  substance  has  been  shown  to  be  a  specific 
but  complex  chemical  compound.  It  may  be  seen  under  the 
microscope  as  granules  clustered  within  the  cells  of  some  green 
plant  tissues.  In  some  colorless  fungi  and  lower  plants  it  is 
lacking.  Such  plants  do  not  construct  organic  compounds  in- 
dependently but  derive  them  from  previously  existing  vegetation. 
The  green  color  of  plants  is  due  to  chlorophyll,  as  may  be  shown 
by  extracting  it  with  alcohol.  Such  an  extract  is  intense  green 
in  color,  due  to  the  chlorophyll  removed  by  the  alcohol,  while 
the  extracted  tissue  is  bleached  and  colorless.  In  some  unex- 
plained manner  this  sensitive  compound,  under  the  influence  of 
light,  induces  the  union  of  carbon  dioxide  assimilated  from  the 
air  and  water  conveyed  from  the  root,  with  the  production  of 
the  first  carbohydrates  of  the  plant. 

It  is  not  known  whether  this  first  product  is  starch,  sugar,  or 
a  simple  precursor  of  these  compounds.  The  process  involves 
the  elimination  of  two  parts  of  oxygen  for  each  part  of  carbon 
dioxide  assimilated,  as  shown  by  the  following  general  equation : 

6C02    +     6H2O   =   C6H12O6  +  602 
carbon  dioxide      water        carbohydrate      oxygen 
The  evolution  of  oxygen  in  this  process  has  been  proved  by 
experiments  in  which  living  leaves  were  confined  in  inverted 
jars  of  water.    A  gas  which  collected  above  the  water  responded 
to  tests  for  oxygen  and  its  volume  was  found  to  be  equivalent  to 
the  carbon  dioxide  taken  up. 


The  Plant  93 

The  plant  also  performs  through  the  leaves  the  process  of 
respiration  in  which  oxygen  of  the  air  combines  with  compounds 
of  the  plant,  with  an  accompanying  elimination  of  carbon  di- 
oxide. This  process  is  most  evident  in  darkness  since  it  is  not 
masked  then  by  the  more  extensive  process  of  carbon  dioxide 
assimilation.  By  combining  the  carbohydrates  as  a  basal  ma- 
terial with  nitrogen  and  sulphur  brought  from  the  soil,  the  leaf 
cells  produce  a  further  class  of  organic  compounds  known  as 
proteins.  Nitrogen  and  sulphur  usually  enter  the  plant  as 
highly  oxidized  compounds  and  are  built  into  the  proteins  after 
suffering  reduction  or  loss  of  oxygen. 

The  leaf  functions  also  as  a  temporary  reservoir  for  migratory 
compounds  which,  at  the  death  of  this  organ,  return  into  the 
general  circulation  of  food  materials  in  the  plant.  This  is  true 
particularly-  of  trees  and  other  perennial  plants,  whose  dead 
leaves  are  skeletons  consisting  chiefly  of  cellulose  compounds  and 
unessential  ash  constituents  like  silica,  the  more  important  nu- 
trient compounds  and  ash  materials  having  returned  to  the  stem 
of  the  plant. 

Flowers,  fruits,  and  seeds  are  pre-eminently  seats  of  construc- 
tive processes  in  which  chemical  reactions  are  especially  active 
and  significant.  Fragmentary  protein  structures,  possibly  the 
amino-acids,  are  here  withdrawn  from  solution  in  the  sap  cur- 
rent and  retained  as  finished  proteins.  Soluble  carbohydrates 
are  converted  to  starch  or  to  some  of  the  fats,  which  are  present 
in  the  seeds.  Ash  constituents  for  the  young  plant  of  the  next 
generation  are  stored  away  as  constituents  of  organic  compounds. 
Absorption  of  oxygen  is  especially  marked  in  these  organs  and 
may  be  accompanied  by  considerable  heat  production.  In  the 
case  of  the  Italian  amm  lily  it  has  been  observed  that  the  large 
pistil  absorbs  in  one  hour  nearly  30  times  its  volume  of  oxygen 
with  a  resultant  temperature  to  over  100°  Fahr. 

The  end  of  all  this  activity  is  the  production  of  mature  seed 
containing  a  finished  plant  embryo,  a  store  of  food  materials,  and 
enzymes  to  inaugurate  the  process  of  germination.  At  this  stage 


94  Agricultural  Chemistry 

of  growth,  the  leaves,  stems  and  roots  are  contributing  their  re- 
serves for  the  production  of  seed.  Migration  of  food  constituents, 
especially  of  starch,  nitrogen  compounds  and  ash  constituents, 
from  the  roots  or  leaves  now  assumes  prominence.  While  the  ash 
constituents  accumulate  in  the  seed  only  in  small  amounts,  suf- 
ficient for  the  growth  of  a  vigorous  seedling,  some  of  the  organic 
reserve  compounds  may  be  stored  in  excess,  giving  distinctive 
character  to  the  seed.  This  is  true  of  starch,  which  gives  the 
cereal  grains  peculiar  value  for  the  manufacture  of  foodstuffs 
and  of  alcoholic  products.  It  is  also  true  of  fats  and  proteins, 
which  give  to  cotton  and  flaxseed  high  commercial  values  as 
sources  of  oils  and  as  protein-furnishing  constituents  of  rations 
for  live  stock.  Starch  and  fat  serve  the  young  seedling  as  sources 
of  energy  for  growth  and  as  material  for  carbohydrate  construc- 
tion until  it  becomes  independent  of  the  seed;  the  proteins  of 
the  seed  furnish  simple  nitrogenous  structures  from  which  the 
proteins  of  the  seedling  are  formed. 

Compounds  of  the  plant.  As  a  result  of  the  activity  of  the 
various  plant  organs,  there  is  produced  a  great  variety  of  com- 
pounds, partly  transitory  in  nature  and  partly  of  permanent 
character.  The  following  classification  is  a  brief  plan  of  division 
for  the  compounds  of  the  plant: 

f  Carbohydrates 
Water  -        Non-        j  Fats  and  waxes 

I  Nitrogenous  *j  Terpenes  and  essential  oils 
.Organic  or  corn-  (.Organic  acids 


..  - 

bustible  matter  ]  f  Proteins 


Dry  Matter   \ 

I  Amines  and  alkaloids 
Ash  containing    |  Salts  of  organic  acids 
compounds      \  Inorganic  compounds 

Water  holds  a  place  in  the  chemistry  of  the  plant  the  import- 
ance of  which  can  hardly  be  realized.  Besides  its  physical  func- 
tions of  transporting  food  materials  and  regulating  the  tempera- 
ture of  the  plant,  it  is  responsible  for  maintaining  the  turgidity 


The  Plant  95 

of  the  individual  cells,  thus  giving  form  and  rigidity  to  immature 
and  succulent  growth.  The  entrance  of  many  comparatively  in- 
soluble compounds  into  the  plant  is  made  possible  when  they 
assume  a  hydrated  form,  that  is,  when  they  are  combined  with 
water.  Silicon,  for  example,  which  forms  comparatively  insol- 
uble soil  compounds,  is  supposed  to  enter  the  plant  as  silicic  acid, 
which  through  dehydration  or  loss  of  water  becomes  deposited 
as  silica.  Water  is  the  chief  constituent  in  green  plants,  its 
amount  varying  from  80  per  cent  in  grasses  to  90  per  cent  in  root 
crops.  Its  amount  decreases  at  the  maturing  stage.  For  ex- 
ample, timothy  grass,  which  contains  on  the  average  80  per  cent 
of  water,  has  when  dead  ripe  63  per  cent  of  this  constituent. 

The  importance  of  water  in  the  transformation  of  carbohy- 
drates will  be  shown  in  following  paragraphs.  It  is  important 
to  observe  here  that  the  constituents  of  water  form  55.5  per  cent 
of  starch  and  that  their  proportion  is  equally  prominent  in  other 
carbohydrates.  Water  bears  similar  importance  in  the  structure 
and  transformations  of  all  the  other  plant  compounds. 

The  carbohydrates  form  a  widely  distributed  and  prominent 
group  of  compounds  in  the  plant  kingdom.  They  may  be  classed 
in  order  of  increasing  complexity  as  follows: 

Mono-saccharides.     C0H1206. 

Di-saccharides.     C12H22On. 

Tri-saccharides.     C18H32O16. 

Poly-saccharides.     (CcH1005)n. 

Mono-saccharides  are  commonly  represented  by  dextrose  or 
glucose,  CCH]2O6,  which  occurs  in  most  fruits.  Artificial  dex- 
trose or  ' '  glucose  syrup ' '  is  prepared  commercially  by  the  action 
of  hot,  dilute  sulphuric  acid  upon  starch  and  subsequent  removal 
of  the  acid  by  means  of  lime.  This  is  a  hexose  or  six-carbon 
sugar,  being  composed  of  six  parts  of  carbon  combined  with  the 
equivalent  of  six  parts  of  water.  This  structure,  to  which  the 
name  carbohydrate  (signifying  carbon-water  union)  owes  its 
origin,  may  be  confirmed  by  gently  heating  the  sugar  in  a  glass 
tube.  Water  separates  from  the  compound  and  collects  on  the 


96  Agricultural  Chemistry 

adjacent  cold  surface  of  the  tube,  while  the  remaining  blackened 
or  charred  portion  denotes  the  presence  of  carbon.  Glucose  is  a 
product  of  the  decomposition  of  all  higher  carbohydrates.  It  is 
about  two-thirds  as  sweet  as  common  sugar. 

Levulose  or  fructose,  C6H12O6,  is  a  mono-saccharide  of  the 
same  general  composition  as  dextrose  and  has  many  properties 
in  common  with  it.  The  two  sugars  are  commonly  associated  in 
fruits.  Levulose  is  abundant  in  honey  where  it  exceeds  the 
amount  of  dextrose,  the  two  forming  about  75  per  cent  of  the 
product. 

No  other  hexose-sugars  occur  free  in  plants,  but  galactose  is  a 
compound  of  this  class.  It  is  formed  by  hydrolysis  or  addition 
of  water  to  a  group  of  poly-saccharides,  called  galactans,  which 
occur  in  plants. 

Di-saccharides  are  represented  in  the  plant  kingdom  by  two 
sugars.  Sucrose,  or  cane  and  beet  sugar,  C12H22O11,  occurs  in 
many  plants,  notably  in  the  juice  of  sugar  cane  (16  to  18  per 
cent),  in  the  sugar  beet  (10  to  18  per  cent),  and  in  the  sap  of 
the  sugar  maple  (about  90  per  cent  of  the  solids).  The  sweet- 
ness of  the  sap  of  corn  and  sorghum  stalks  and  of  peas  and  other 
seeds  is  due  to  appreciable  amounts  of  sucrose.  This  sugar  dif- 
fers from  the  mono-saccharides  in  that  it  crystallizes  readily,  and 
this  property  is  taken  advantage  of  in  purifying  the  commercial 
product.  By  the  action  of  the  enzyme  invertin,  which  occurs  in 
yeast,  sucrose  is  converted  into  equal  parts  of  dextrose  and  levu- 
lo.se,  hence  the  designation  ' '  di-saccharide. " 

This  process  of  "inversion"  may  be  accomplished  also  by  boil- 
ing sucrose  with  dilute  acids,  the  product  by  both  methods  being 
known  as  "invert  sugar."  The  change  involves  the  addition  of 
one  part  of  water  to  each  part  of  cane  sugar  and  this  reaction 
characterizes  the  inter-relations  of  carbohydrates  in  general, 
which  are  largely  dependent  upon  differences  in  content  of  the 
water-forming  elements,  thus: — 

C11HM01i+H,0=C6H110.+C.H110. 


The  Plant  97 

Maltose  or  malt  sugar,  C^H^O^.H^  is  a  di-saccharide  oc- 
curring in  small  amounts  in  seeds.  Its  amount  is  considerably 
increased  as  a  result  of  germination,  in  which  the  enzyme  known 
as  diastase  converts  starch  to  dextrines  and  maltose.  Crystal- 
lized maltose  contains  one  part  of  water.  This  makes  possible  a 
direct  conversion  to  lower  sugars,  and  upon  inversion  by  enzymes 
or  acids  one  part  of  this  sugar  yields  two  parts  of  dextrose. 

Tri-saccharides  are  represented  in  plants  by  raffinose,  C18H32- 
016.5H2O.  This  sugar  occurs  in  cotton  seed  and  the  embryos 
of  wheat,  barley  and  other  seeds.  It  sometimes  occurs  in  sugar 
beets,  especially  as  a  result  of  disease  or  injury,  and  in  quantity 
sufficient  to  interfere  with  the  refining  of  the  beet  sugar.  Eaf- 
finose  inverts  to  equal  parts  of  dextrose,  levulose  and  galactose. 

Poly-saccharides  are  the  most  abundant  of  the  carbohydrates. 
Starch,  (C6H10O5)n,  which  is  one  of  the  simpler  members  of  this 
group  of  compounds,  is  an  unknown  multiple  of  a  chemical  group 
containing  six  parts  of  carbon  and  the  equivalent  of  five  parts  of 
water.  It  may  be  considered  as  a  multiple  of  the  compound 
dextrose,  in  which  each  part  of  dextrose  has  lost  one  part  of 
water.  Diastase  of  sprouting  seeds  and  the  enzyme  ptyalin, 
which  occurs  in  saliva,  convert  starch  to  a  mixture  of  simpler, 
gummy  carbohydrates,  known  as  dextrines  and  then  to  maltose. 

Hot,  dilute  acids  invert  starch  completely  to  dextrose  and  by 
this  means,  in  addition  to  the  action  of  diastase,  the  chemist  de- 
termines the  amount  of  starch  in  plants.  This  process  is  also, 
as  has  been  stated,  the  basis  for  the  commercial  production  of 
corn  syrup  or  glucose  syrup  thus : — 

(C6H1005)n+N(H20)=N(C6H1206) 
starch  water  sugar 

The  large  amounts  of  starch  in  cereal  grains,  as  barley  and  corn, 
and  in  some  root  crops,  as  the  potato,  give  them  value  for  the 
production  of  alcohol  and  alcoholic  liquors.  Alcohol  is  not 
formed  directly  from  starch,  but  is  a  product  of  the  fermenta- 


98  Agricultural  Chemistry 

tion  of  the  sugars  to  which  starch  may  be  converted  by  malt 
extract : — 

C0H]2Ott+yeast=2C02+2C2HBOH 
sugar  carbon        alcohol 

dioxide 

The  amounts  of  starch  found  in  some  plants  and  plant  prod- 
ucts are  as  follows,  expressed  in  per  cent  of  the  air  dried  material : 

Per  cent  Per  cent 

Wheat  flour    66.55    Rice   grain    ".  79.4 

Corn   meal    71.00    Barley  grain    62.0 

Corn  plant   (ears  glazed)..  15.40    Potato   tuber    75.5 

Corn   stover    0.96    Bean  grain   42.7 

Oat  meal   56.23    Pea  grain 40.5 

Some  of  the  grains  and  roots  named  above  are  familiar  as 
sources  of  commercial  starch.  This  is  true  of  corn  and  the  po- 
tato. Tapioca  is  a  starch  preparation  from  the  root  of  the  cas- 
sava plant  and  sago  starch  is  taken  from  the  interior  of  'the 
trunk  of  the  sago  palm.  A  single  tree  of  the  latter  variety  may 
yield  500  pounds  of  sago. 

Individual  starch  granules  are  readily  detected  in  plant  cells 
by  means  of  the  microscope  and  under  these  conditions,  the  char- 
acteristic markings  of  the  granules  of  different  plants  become  of 
value  in  identifying  the  source  of  the  sample. 

Dextrine  of  commerce  is  a  mixture  of  compounds  varying  in 
complexity.  Its  gummy  nature  gives  it  value  as  an  adhesive 
paste.  Stick-labels  and  postage  stamps  are  coated  with  dextrine. 
Mixtures  of  dextrines  occur  in  the  grains  of  cereal  plants  and 
their  amount  increases  at  germination  as  a  result  of  the  decom- 
position of  starch.  The  relative  proportions  of  chemical  elements 
in  starch  and  the  dextrines  are  the  same,  but  the  latter  are  ap- 
parently simpler  groups  of  a  basal  compound  (C0H1006),  as- 
cending in  complexity  toward  the  composition  of  starch.  Dex- 
trines are  precursors  of  the  simple  carbohydrate  maltose,  which 
occurs  in  germinated  grains. 


Galactans  are  complex  poly-saccharides  occurring  particularly 
in  the  seeds  of  leguminous  plants,  in  some  of  which  they  are  the 
chief  carbohydrates.  In  the  process  of  hydrolysis,  these  com- 
pounds combine  with  water  to  form  the  comparatively  simple 
hexose  known  as  galactose,  C6H1206. 


Starch  granules  from  various  sources 

Cellulose  (C6H1005)n,  the  basal  constituent  of  woody  fibre, 
is  a  poly-saccharide  of  great  importance  for  its  tenacity  and 
rigidity,  which  give  form  and  resistance  to  the  walls  of  mature 


100  Agricultural  Chemistry 

plant  cells.  It  rarely  occurs  free  in  the  plant,  but  rather  as  a 
constituent  of  compound  celluloses,  such  as  the  incrusting,  ligni- 
fied  celluloses  or  ligno-celluloses  of  cell  walls.  Cotton  and  hemp 
fibres  are  single,  elongated  plant  cells,  whose  walls  are  composed 
of  nearly  pure  cellulose.  By  treating  these  fibres  successively 
with  hot,  dilute  acid,  with  hot,  dilute  alkali  and  finally  with 
chlorine  gas,  and  washing  out  the  products  formed,  the  purest 
known  cellulose  has  been  obtained.  It  is  evident  that  to  resist 
such  treatment  this  compound  must  be  extremely  stable.  It  can 
be  brought  into  solution,  however,  by  certain  reagents,  and  when 
treated  with  strong  sulphuric  acid,  followed  by  diluting  with 
water  and  'boiling,  it  is  broken  down  and  partially  converted  to 
dextrose. 

This  brief  discussion  of  the  properties  of  the  various  carbo- 
hydrates in  connection  with  their  common  products  of  decompo- 
sition, may  serve  to  indicate  a  common  basis  of  structure  for  this 
group  of  plant  compounds.  Thus,  by  the  union  of  two  mono- 
saccharides,  we  have  a  di-saccharide.  An  addition  of  another 
simple  sugar  produces  a  tri-saccharide.  Further  increments  re- 
sult in  dextrines  of  increasing  complexity  and  decreasing  solu- 
bility until  we  have  as  a  product,  starch.  This  is  a  substance 
insoluble  in  cold  water  and  decomposed  with  some  difficulty. 

By  some  internal  re-arrangement  of  the  chemical  elements  in- 
volved in  the  carbohydrate  molecule,  we  may  have  cellulose  pro- 
duced instead  of  starch.  This  is  an  extremely  resistant  and 
comparatively  permanent  compound  in  which  apparently  the 
stability  of  the  carbohydrates  has  reached  a  maximum.  These 
constructive  processes  take  place  only  in  the  plant.  "We  can  fol- 
low them  in  the  chemical  laboratory  only  in  a  reversed  order, 
proceeding  from  the  complex  to  the  simple.  Our  knowledge  is 
therefore  concerned  with  the  general  relations  of  these  com- 
pounds, rather  than  with  the  actual  changes  by  which  they  are 
successively  produced  in  the  plant. 

The  pectin  substances  and  pentosans  should  be  classed  under 
the  general  head  of  carbohydrates. 


The  Plant  101 

Pectins,  C38H48032(  ?),  are  insoluble  bodies  which  occur  in  the 
flesh  of  most  unripe  fruits.  Upon  boiling  with  water  they  yield 
various  poorly  defined  compounds  of  gelatinous  nature,  some- 
times referred  to  as  pectoses  or  pectic  acids.  It  is  to  these  bodies 
that  the  ''setting"  of  fruit  jellies  is  due.  On  treatment  with 
weak  acids  or  alkalies,  they  yield  simple  sugars,  thereby  disclos- 
ing their  carbohydrate  nature.  Besides  dextrose,  they  yield  a 
class  of  sugars  containing  five  parts  of  carbon  and  hence  des- 
ignated as  pentoses,  C5H1005.  The  mucilaginous  substances  of 
flaxseed,  quince  fruit  and  parts  of  many  other  plants,  are  of 
pectin  nature. 

Pentosans,  (C5H804)n,  are  present  in  considerable  amounts  in 
certain  gummy  exudations  of  plants,  such  as  cherry  gum,  which 
oozes  from  wounds  on  trees  of  the  prunus  genus,  and  gum  arabic 
of  tropical  Acacias,  a  genus  of  leguminous  plants.  The  pento- 
sans  of  gum  arabic  yield  on. 'hydrolysis;  a  pentose  sugar  called 
arabinose,  Cr,H10(X.  '  'Xylose  i's  .a  pcntosp^sugar  'obtained  from  the 
so-called  wood  guHisV  or  pentosans  which  are  ai>imdant  in  straws 
and  some  grains!  The  penipsans  , are,  intimately  associated  with 
the  cellulose  of  plant  iissn^."!  iPii^y.  ddtfefc'  from  tfyeir  correspond- 
ing sugars.,'  tie-  -per toses,  by  the  equivalent  -of' ^ne'-part  less  of 
water.  Upon'  boiliii^  ,wi,th  dilute,  rfuaeral  'acids  each  of  these 
compounds  takes  on 'one J,jJart- 'of 'water.'  Araban  yields  arab- 
inose readily,  while  xylan  yields  xylose  only  gradually  under 
these  conditions,  thus: — 

(C5II804)n+N(H20)=N(C5H1005) 
pentosan  water  pentose 

This  behaviour  demonstrates  the  carbohydrate  nature  of  the 
bodies  under  consideration.  The  following  percentages  of  pen- 
tosans have  been  found  in  some  plant  materials : — 

Hays   20  per  cent 

Gluten  feed   17        " 

Linseed  meal    13        " 

Brewers'  grains   24         " 

Wheat  bran  .  .  24        " 


102  Agricultural  Chemistry 

From  60  to  90  per  cent  of  these  compounds  in  feeding  stuffs 
disappears  from  the  digestive  tract  of  herbivora.  This  may  be 
partly  due  to  bacterial  fermentation.  Since  pentosans,  when 
assimilated  by  the  animal,  appear  to  have  a  value  similar  to  that 
of  starch,  it  is  evident  that  in  some  cases  they  may  be  of  con- 
siderable importance  as  constituents  of  the  carbohydrate  material 
of  feeding  stuffs. 

Fats  are  uniform  in  their  general  composition,  consisting  of 
one  part  of  glycerine,  C3H,,(OH)3,  combined  with  three  parts  of 
fatty  acid.  The  latter  constituent  controls  the  nomenclature  of 
the  fats.  Thus,  for  example,  the  fat  containing  three  parts  of 
stearic  acid,  C17H3.COOH,  is  known  as  "trl-stearin,"  or  more 
commonly  as  "stearin,"  C3H5(COOC17H35)3.  Fats  which  con- 
tain two  or  three  different  fatty  acids  in  combination  with  the 
same  part  of  glycerine  are  called  "mixed  glycerides. "  Acetic 
acid,  CH3COOH,  which  causes  the  sour  taste  in  vinegar,  is  a 
typical  example  of  the,  fatty  acids,  the  simpler  members  of  this 
group  of  compomids  being  volatile  liquids  of  characteristic,  pun- 
gent odor  similar  to  that  of  the  acid  cited.  The  higher  members 
of  the  acetic  a.eid  series  are  solid  siibetances ;  and  the  fats  in  which 
they  occur  are 'also  solid,  in  distinction  from  liquid  fats  or  oils 
produced  by  lower  fatty  acids  These  acids  rarely  occur  free,  as 
in  the  case  of  formic  aci'd.,  which  produces  the  sting  of  the  nettle 
plant;  but  they  usually  occur  as  constituents  of  neutral  fats. 
Oleic,  C]7H33COOH,  linoleic,  C17H31COOH,  and  linolenic  acids, 
C17H2nCOOH,  are  types  of  three  other  series  of  fatty  acids  which 
are  more  abundant  in  plants  than  the  acetic  acid  series.  In  dis- 
tinction from  the  latter,  these  acids  are  characterized  by  loose 
chemical  bonds,  by  virtue  of  which  their  fats  take  on  oxygen, 
iodine  and  other  active  chemical  elements.  The  constitution  of 
oleic  acid  may  be  written  as  follows,  showing  the  double  bonds 
between  the  carbon  atoms,  which  is  the  point  of  unsaturation : — 
CH3(CH2)7CH=CH(CH2)7COOH.  Thus,  on  prolonged  expos- 
ure to  air,  oleic  acid  takes  up  one  part  of  oxygen,  linoleic  acid 
takes  up  two  parts  and  linolenic  acid  takes  up  three  parts,  by 


The  Plant  103 

weight.  This  change  is  accompanied  in  proportion  to  its  extent 
by  "setting"  or  hardening  of  the  oils  concerned.  As  a  result, 
while  olein  remains  liquid  even  when  exposed  to  the  air  in  thin 
layers  and  is  characterized  as  a  non-drying  oil,  increasing  propor- 
tions of  linolein  and  linolenin  produce  consecutively  the  semi- 
drying  and  drying  oils. 

The  high  percentages  of  the  latter  oils  in  linseed  oil  enhance 
its  value  as  a  vehicle  for  paints,  because,  having  distributed  the 
pigments  which  it  carries,  it  gradually  "sets"  and  forms  a  du- 
rable protective  coating.  If  the  process  of  oxidation  in  such  an 
oil  is  hastened  .by  exposing  it  in  thin  layers  upon  inflammable 
material,  sufficient  heat  may  be  generated  to  cause  spontaneous 
combustion.  Ignorance  of  this  fact  has  caused  destructive  fires, 
due  to  oil  soaked  rags  and  similar  material. 

Plant  fats  consist  for  the  most  part  of  mixtures  of  olein  and 
linolein  with  smaller  amounts  of  stearin,  palmitin  and  lower 
members  of  the  acetic  acid  series.  The  proportions  of  fats  are 
such  as  to  maintain  a  liquid  state  at  ordinary  temperatures  and 
produce  the  oils  of  the  seed  of  cotton,  castor  bean,  flax  and  other 
plants.  The  simple  fats  differ  from  carbohydrates  by  a  higher 
content  of  carbon  and  hydrogen  and  lower  oxygen  content  than 
the  latter.  This  higher  content  of  combustible  elements  renders 
fats  of  greater  fuel  value  than,  the  other  leading  plant  compounds,. 
because  of  greater  oxygen  consumption  during  combustion.  This 
property  assumes  great  importance,  as  a  source  of  heat  or  energy, 
when  the  fats  are  oxidized  in  the  sprouting  seed  or  in  the  animal1 
body. 

In  some  remarkable  manner,  the  plant  reverses  this  process  and' 
constructs  its  fats  from  carbohydrates  with  elimination  of  oxy~ 
gen.  The  following  figures  show  the  relative  composition  of  a 
typical  carbohydrate  and  a  typical  fat. 

Per  cent  Per  cent  Per  cent 

Carbon  Hydrogen  Oxygen 

Carbohydrate  (starch)   39.98  6.71  53.31 

Fat  (stearin)  76.78  12.4S  10.77 


104  Agricultural  Chemistry 

Fats  occur  in  plants  chiefly  as  reserves  in  the  seed.  The  seeds 
of  cereal  plants  such  as  corn  and  oats  contain  only  small  amounts 
of  fat.  Flaxseed,  cotton-seed,  the  castor  bean  and  other  seeds 
contain  oil  in  sufficient  amount  to  render  its  extraction  on  a  com- 
mercial scale  both  feasible  and  profitable.  The  fat  content  of 
some  common  seeds  is  as  follows : — 

Per  cent  Per  cent 

Barley 1.8    Cotton  20.0 

Wheat  2.0    Sunflower 21.0 

Corn    5.0    Flax 33.5 

Oats  5.0    Castor  bean 50.0 

The  old  fashioned  home  process  of  soap-making  by  boiling 
waste  grease  with  leachings  from  wood  ashes  depends  upon  the 
fact  that  alkali  metals,  in  this  case  the  potassium  or  " potash"  of 
wood  ashes,  will  displace  glycerine  from  fats,  thus: — 

C3H5  ( COOC17H35)  3+3KOH=C3H5  ( OH)  3+3C17H35COOK 
fat  alkali         glycerine  soap 

Super-heated  steam  also  breaks  up  fats  into  glycerine  and  fatty 
acids,  and  in  common  with  the  alkali  treatment  mentioned  above, 
the  process  is  called  saponification.  The  glycerine  of  commerce 
is  a  by-product  from  this  process  in  the  soap  industry.  Since 
mineral  oils  cannot  be  saponified,  we  have  here  a  means  of  dis- 
tinguishing them  from  fats. 

Lecithin,  C44H9009NP,  is  a  compound  closely  related  to  the 
fats.  In  place  of  one  part  of  fatty  acid  in  a  normal  fat  it  con- 
tains phosphoric  acid  combined  with  a  nitrogen-containing,  basic 
compound  known  as  choline.  Lecithin  is  sometimes  referred  to 
as  a  " phosphorized  fat."  It  occurs  in  the  seeds  of  cereals  and 
to  a  greater  extent  in  the  seeds  of  legumes. 

Waxes  have  some  properties  in  common  with  the  fats  and  are 
frequently  associated  with  them  in  the  plant  and  separated  with 
them  by  methods  of  extraction.  They  differ  from  fats  in  that 
they  contain  an  alcohol  of  higher  weight  in  place  of  glycerine, 
this  alcohol  being  combined  with  the  fatty  acid  in  equal  parts. 
Bees-wax  consists  chiefly  of  the  palmitic  ester  of  myricyl  alcohol, 


The  Plant  105 

Ci5II3iCOOC30H61.  Chinese  wax  and  the  carnauba  wax  obtained 
from  the  leaves  of  a  South  American  palm  are  single  compounds, 
while  the  waxes  found  in  the  seeds  of  the  palm,  flax,  cotton  and 
other  plants  are  mixtures.  The  "bloom"  of  leaves  and  fruits, 
which  serves  as  a  protective  coating,  is  composed  of  waxes.  These 
compounds  can  be  converted  to  soaps  in  the  same  manner  as  fats, 
but  they  yield,  of  course,  other  alcohols  in  place  of  glycerine. 

Terpenes,  essential  oils,  camphors  and  resins  form  another 
group  of  closely  related  plant  compounds.  The  terpenes  belong 
to  a  class  of  chemical  compounds  known  as  hydro-carbons,  which 
are  composed  of  the  elements  carbon  and  hydrogen  only,  (C5H8)n. 
They  are  partly  liquids,  such  as  spirits  of  turpentine,  and  partly 
solids,  such  as  rubber  and  gutta-percha.  As  in  the  case  of  car- 
bohydrates, a  classification  of  these  bodies  in  order  of  complexity 
is  in  use  which  separates  them  into  mono-,  di-  and  poly-terpenes. 
Terpenes  are  products  of  pitch  yielding  trees.  Turpentine  is  a 
terpene  of  special  value  in  the  paint  industry  as  a  "thinner" 
or  solvent  for  fats  and  oils. 

The  essential  oils  to  which  the  characteristic  odors  of  flowers 
and  flavors  of  fruits  are  due  are  partly  hydro-carbons,  as  in  the 
case  of  oil  of  turpentine  and  oil  of  lavender.  Others,  such  as  oil 
of  wintergreen  and  almond  oil,  contain  some  oxygen.  Almond 
oil  is  benzoic  aldehyde,  C6H5CHO.  Heliotropin  of  the  helio- 
trope and  the  compounds  to  which  the  aromas  of  the  banana, 
orange  and  other  fruits  are  due,  are  essential  oils.  The  pleasing 
smell  of  new  mown  hay  is  due  to  the  essential  oil,  coumaiin, 
C9H002.  These  compounds  are  of  value  in  the  compounding  of 
perfumes,  cordials  and  medicines.  They  are  of  special  signific- 
ance in  foods  because  of  their  probable  effect  on  palatability. 

Camphors,  C10H160,  are  obtained  by  the  distillation  of  certain 
tropical  woods.  They  differ  from  terpenes  in  containing  oxy- 
gen added  to  the  elements  of  the  latter.  The  two  classes  of 
compounds  are  apparently  closely  related  products  of  the  chem- 
ical processes  of  the  plant. 


106  Agricultural  Chemistry 

Resins  occur  in  pitches  and  are  closely  allied  in  composition  to 
the  camphors.  Like  terpenes  and  camphors  they  may  be  distin- 
guished from  fats  by  failure  to  produce  soaps  by  the  usual 
process  of  saponification. 

Organic  acids  often  occur  in  plants  in  considerable  amounts 
and  are  responsible  for  the  sour  taste  frequently  observed.  They 
are  produced  by  the  fermentation  of  carbohydrates  and  rarely 
occur  free  but  usually  as  acid  or  neutral  salts  of  potassium  or 
calcium.  The  sourness  of  lemons  is  due  to  citric  acid,  C3H4OH- 
(COOH)3.H2O.  The  acid-potassium  salt  of  oxalic  acid,  (COOH)2, 
occurs  in  sorrel  and  acid-calcium  oxalate  has  been  found  in  rhu- 
barb. Malic  acid,  C,H3OH(COOH),,  is  common  in  fruits,  and 
exists  as  the  acid-potassium  salt  in  rhubarb  and  the  acid-calcium 
salt  in  the  berries  of  the  mountain  ash,  tobacco  leaves  and  other 
plants.  The  acid-potassium  salt  of  tartaric  acid,  C,H2(OH)2- 
(COOH)2,  is  characteristic  of  the  grape,  and  potassium  and  cal- 
cium salts  of  this  acid  are  found  in  the  pine-apple,  sumac  berry 
and  other  fruits.  It  is  interesting  to  note  in  this  connection  as 
suggesting  a  possible  source  of  these  acids  in  plants,  that  lactic 
acid,  CH3CHOH.COOH,  develops  in  corn  silage  as  a  product  of 
hydrolysis  of  dextrose  and  other  carbohydrates.  These  acid  com- 
pounds play  an  important  part  in  the  production  of  character- 
istic flavors. 

The  proteins  are  compounds  of  the  greatest  importance  in  the 
plant.  They  are  of  complex  structure,  containing  not  only  car- 
bon, hydrogen  and  oxygen,  ~bui  also  nitrogen  and  sulphur.  This 
large  number  of  constituents  makes  possible  a  variety  and  com- 
plexity of  structure  fitting  them  for  the  delicate  and  complicated 
reactions  which  characterize  life  processes.  Proteins  form  the 
basis  of  the  life-bearing  protoplasm  and  nucleus  of  each  plant 
cell.  Although  contained  in  every  cell,  they  are  localized  chiefly 
in  the  seed  and  furnish  nitrogen  for  the  first  protein  structures 
of  the  seedling.  Individual  proteins  are  characterized  by  a  con- 
tent in  fixed  proportion  of  the  simpler  nitrogenous  bodies  known 
as  amino-acids.  The  simplest  of  these  amino  acids  is  amino- 


The  Plant  107 

acetic  acid,  commonly  called  glycocoll  or  glycin,  CH2NH2.COOH. 
Asparagin,  which  is  a  derivative  of  an  amino-acid,  occurs  in 
freshly  sprouted  asparagus,  peas  and  beans.  It  is  produced  from 
seed  proteins  by  enzyme  action  and  is,  in  part,  eventually  fitted 
into  the  proteins  of  the  seedling. 

Plant  proteins  may  be  classified  briefly  as  follows : 

1.  Albumins:  Soluble  in  pure  cold  water;  coagulated  by  boil- 
ing; occur  in  seeds  only  in  small  amounts. 

2.  Globulins:  Insoluble  in  water;   soluble   in   salt  solutions; 
separate  out  on  diluting  or  saturating  the  solution.     Most  com- 
mon and  abundant  of  plant  proteins.     Occur  in  largest  amount 
in  the  seeds  of  leguminous  plants.     Certain  globulins  appear  to 
be  characteristic  of  the  seed  in  which  they  are  found,  as  with 
avenalin  of  the  oat,  maysine  of  corn,  and  hordein  of  barley. 
Edestin,  -the  globulin  of  the  hemp  seed,  however,  occurs  in  sev- 
eral grains. 

3.  Alcohol  soluble  proteins:  (Prolamins).     Nearly  or  wholly 
insoluble  in  water;  soluble  in  alcohol  of  from  70  to  90  per  cent 
strength.     They  have  been  found  only  in  the  seeds  of  cereal 
plants. 

4.  Glutelins:  Not  dissolved  by  water,  salt  solutions,  or  alcohol; 
may  be  extracted  by  treating  the  residue  of  seeds  from  which  the 
other  proteins  have  been  removed,  with  dilute  alkaline  solutions. 
Isolated  and  purified  with  much  difficulty.     The  only  well  de- 
fined glutelins  are  glutenin  of  the  seed  of  wheat  and  orysenin  of 
the  seed  of  rice. 

5.  Conjugated  (compound)  proteins:  These  proteins  have  been 
modified  by   combining  with   other   compounds.     They   include 
nucleo-proteins,  in  which  a  large  proportion  of  protein  is  com- 
bined with  a  small  amount  of  nucleic  acid.     Phosphorus  is  pres- 
ent in  these  compounds,  being  contributed  by  the  nucleic  acid. 
Conjugated  proteins  of  other  types  occur  in  the  animal  kingdom, 
but  the  exact  nature  of  other  preparations  than  nucleo-proteins 
from  plants,  assigned  to  this  group  of  compounds,  has  not  been 
clearly   established.     Such   knowledge   as   we   possess  indicates 
that  only  small  quantities  of  nucleo-proteins  occur  in  the  entire 


108 


Agricultural  Chemistry 


seed  and  that  they  are  chiefly  in  the  tissues  of  the  embryo,  in 
which  the  nuclei  of  cells  are  most  abundant. 

The  approximate  amounts  of  some  plant  proteins  found  in 
seeds  are  given  by  Osborne  as  follows : 


Protein 

Source 

Per  cent  in  the 
dry  material 

Albumins 
Leucosin  

0.3  -0.4 

Leucosin 

0  43 

Leucosin                      .   .    . 

Barley  grain  

0.3 

Phaselin            

Kidney  bean  grain  

2.0 

Legumelin  

Pea  meal  (free  from  outer 

seed  coats)               .  .  .... 

2.0 

Legumelin  

Lentil     meal     (free    from 

outer  seed  coats)    ... 

1  25 

Legumelin  

Horse    bean    meal     (free 

Legumelin      .       . 

from  outer  seed  coats).. 

1.5 
1.5 

Globulins 
Mavsin 

•     0.25 

Phaseolin  

Kidney  bean  grain  

20-00 

Avenalin        

Oat  grain  

1.5 

Conglutin 

Yellow  Lupine  grain  

26.2 

Le^umin 

Vetch  grain  

10.0 

Legumin  and  Vicilin  

Pea  meal  (free  from  outer 

10.0 

Legumin  and  Vicilin  

Lentil    meal    (free    from 

outer  coatings)  

13.0 

Legumin  and  Vicilin  

Horse    bean     meal    (free 

Fdestin  . 

from  outer  coatings)  
Corn  grain  

17.0 

0.14 

Edestin 

Wheat  grain  

0.6  -0.7 

Edestin  

Cotton  seed  meal  (oil  free) 

15.83 

Edestin                          .... 

17.6 

Alcohol  soluble  proteins 
Gliadin 

Rye  grain  

4.00 

Gliadin 

Wheat  grain  

4.25 

Hordein 

4.00 

Zein 

5.00 

Glutelins 
Glutenin                  

Wheat  grain  

4.0  -4.5 

Glutenin 

3.5  (assumed) 

Glutenin                           .  .  . 

11.25        " 

Glutenin 

4.50        " 

The  Plant  100 

Amino-acids,  which  have  been  referred  to  as  constituents  of 
proteins,  occur  free  to  a  limited  extent  in  plants.  Their  struc- 
ture is  that  of  fatty  acids  into  which  amino  (NH2)  groups  have 
been  substituted  for  hydrogen  atoms  other  than  those  of  acid 
radicles.  They  are  compounds  of  only  weakly  acid  or  even  of 
basic  properties.  Amino-isovaleric  acid  (valine),  C4H8NH2- 
COOH,  is  a  body  of  this  sort  which  has  been  separated  from 
white  and  yellow  lupine  plants  of  two  to  three  weeks '  age.  Leu- 
cin,  C6H13N02,  which  is  a  substituted  amino-acetic-acid,  occurs 
in  smaller  amounts  with  the  amino-isovaleric  acid.  In  some 
coniferous  seeds  the  amount  of  arginin,  another  amino  acid,  ex- 
ceeds that  of  the  amino  acids  already  mentioned.  Arginin, 
C5H9N2(NH2)2COOH,  is  a  di-amino  acid,  that  is,  it  contains  two 
such  amino  groups.  From  proteins,  by  hydrolysing  with  an  acid, 
some  sixteen  different  amino  acids  have  been  isolated.  They  are 
as  follows: 

Glycine,  C2H5N02  Aspartic  acid,  C4H7N04 

Alanine,  C3H7N02  Glutamic  acid,  C5H9N04 

Valine,  C5HnN03  Arginine,  C6H14N402 

Leucine,  C6H13N02  Lysine,  C6H14N202 

Phenylalanine,  Cgll^NG^  Histidine,  CGH9N302 

Tyrosine,  CoH^NOg  Proline,  C5H9N02 

Serine,  C3H7N03  Oxyproline,  C5H9N03 

Cystine,  C6H12N204S2  Tryptophane,  C^H^N.O,, 

Amides  are  nitrogenous  compounds  of  another  class  which 
have  been  the  object  of  considerable  study  in  their  relation  to 
the  feeding  of  animals.  The  proportion  of  the  total  nitrogen  in 
this  form  at  the  time  of  harvesting  the  plant  is  of  considerable 
importance  because  of  the  probable  difference  in  feeding  value 
of  various  nitrogenous  compounds.  Amides  have  the  structure 
of  organic  acids,  into  which  amino  groups  have  been  substituted 
for  the  hydroxyl  group  of  acid  radicles.  They  are,  as  we  might 
therefore  expect,  neutral,  salt-like  bodies.  They  require  only  the 
addition  of  one  part  of  water  to  the  molecule  to  become  ammo- 
nium salts,  and  may  be  considered  as  derivatives  of  ammonia  as 


110  Agricultural  Chemistry 

well  as  of  acids.  Asparagin,  CHNH2.COOH.CH2CONH2,  is  an 
amide  found  in  many  plants,  as  in  asparagus,  peas  and  beans, 
especially  just  after  sprouting.  Glutamin,  C5H10N203,  which  has 
been  found  in  squash  seedlings  and  beet  juice  with  asparagin, 
is  also  an  amide.  These  are  properly  double  amino  compounds, 
being  amides  of  amino-acids.  They  offer  examples  of  the  pos- 
sible complexity  of  structure  of  organic  nitrogenous  compounds 
even  in  their  simpler  forms.  The  amides  and  amino-acids  which 
occur  at  intermediate  stages  of  the  growth  of  plants,  are  derived 
from  the  disintegration  of  tne  seed  proteins,  or  from  construc- 
tive processes  in  the  leaves  and  are  to  a  greater  or  less  extent 
precursors  of  protein  compounds  in  the  new  seed.  Being  readily 
soluble  in  water,  they  form  ready  means  for  the  transportation 
in  the  sap  of  protein  forming  structures,  and  can  be  placed  at 
the  disposal  of  the  reconstructive  forces  in  the  plant. 

Amines,  or  compound  ammonias,  have  only  a  limited  practical 
importance  as  plant  compounds.  They  are  strongly  basic  com- 
pounds resulting  from  the  replacement  of  one  or  more  atoms  of 
hydrogen  in  ammonia  by  hydrocarbon  radicles,  as  (CH3)3N  (tri- 
methylamine).  The  rank  odor  of  some  plants  as  the  fetid  goose 
foot  and  hawthorn  is  due  to  compounds  of  this  sort. 

Alkaloids  are  basic  organic  compounds  involving  substitution 
of  more  complex  organic  radicles  into  the  ammonia  molecule  than 
is  the  case  with  the  amines.  By  virtue  of  their  basic  structure 
they  combine  with  acids;  the  salts  so  formed  offer  means  of  iso- 
lating and  purifying  these  bodies.  Some  of  the  more  common 
alkaloids  are  nicotine,  C10H14N2,  of  tobacco ;  morphine,  C17H19NO2, 
of  the  poppy;  strychnine,  C21H22N2O2,  brucine,  C23H26N204, 
and  curarine  of  strychnos  wood ;  quinine,  C20H24N202,  of  cinch- 
ona bark;  piperin  of  pepper;  solanin  of  the  potato  and  night- 
shade; and  cocaine,  C17H21N04,  of  the  leaves  of  the  South  Amer- 
ican cocoa  tree.  Some  are  of  medicinal  value  as  stimulants 
(strychnine),  others  act  as  narcotics  (nicotine,  morphine),  and 
still  others  are  virulent  poisons  (curarine,  solanin).  Curarire 
is  the  active  constituent  of  curare  extract  with  which  some  wild 
tribes  poison  their  arrow-tips. 


The  Plant 


11] 


The  ash  constituents  of  the  plant,  usually  relatively  small  in 
amount,  are  for  the  most  part  absolutely  essential  to  its  life 
activities.  The  following  chemical  elements  are  always  found  in 
plant  ash:  calcium,  potassium,  magnesium,  sodium,  iron,  phos- 
phorus, sulphur,  chlorine  and  silicon.  Manganese  and  aluminum 
are  occasionally  present ;  and  zinc,  barium  and  other  metals  some- 
times occur  as  accidental  constituents. 

The  following  brief  table  gives  the  amount  and  composition  of 
the  ash  of  some  typical  plants.  The  subject  will  be  taken  up 
more  in  detail  in  connection  with  the  relative  composition  and 
food  demands  of  crops. 

Composition  of  the  Ash  of  Plants 


Pure 

*  -,U 

Ash  Constituents.      Per  cent  in  the  pure  ash. 

Plant 

Asn 
per 
cent 
in 
dry 

Pot- 
ash 

Soda 

Lime 

Mag- 
nesia 

Iron 
Oxide 

Phos- 
phoric 
Acid 

Sul- 
phur 
tri- 
oxide 

Silica 

Chlor- 
ine 

plant 

KzO 

Na2O 

CaO 

MgO 

Fe2O3 

P20fi 

SO8 

SiO 

Cl. 

Timothy 

(hay)  

6.82 

34.69 

1.83 

8.05 

3.24 

0.83 

11.80 

2.85 

32.17 

5.19 

Clover  (early 

bloom)  .... 

6.86 

32.29 

1.97 

34.91 

10.90 

1.08 

9.64 

3.23 

2.69 

3.78 

Wheat 

(grain).... 

1.96 

31.16 

2.07 

3.25 

12.06 

1.28 

47.22 

0.39 

1.96 

0.32 

Wheat 

(straw)  .  .  . 

5.37 

13.65 

1.38 

5.76 

2.48 

0.61 

4.81 

2.45 

67.50 

1.68 

Oat  (grain)  .  . 

3.12 

17.90 

1.66 

3.60 

7.13 

1.18 

25.64 

1.78 

39.18 

0.94 

Oat  (straw).  . 

7.17 

26.42 

3.29 

6.97 

3.66 

1.16 

4.59 

3.21 

46.69 

4.37 

Potato 

(tuber)  

3.79 

60.06 

2.96 

2.64 

4.93 

1.10 

16.86 

6.52 

2.04 

3.46 

Sugar  beet 

(root)  

3.83 

53.13 

8.92 

6.08 

7.86 

1.14 

12.18 

4.20 

2.28 

4.81 

Corn  (grain) 

1.45 

29.78 

1.10 

2.17 

15.52 

0.76 

45.61 

0.78 

2.  Oil 

0.91 

Corn  (stalks) 

5.33 

36-30 

1.20 

10.80 

5.70 

2.30 

8.30 

5.30 

28.80 

1.40 

The  ash  constituents  of  plants  occurring  in  the  seed  are  present 
there  almost  entirely  as  constituents  of  organic  compounds.    The 


112  Agricultural  Chemistry 

hulls  of  the  oat  and  other  grains,  which  are  not  a  part  of  the 
seed  proper,  have  been  found  to  contain  considerable  amounts  of 
inorganic  compounds,  among  which  silica  is  especially  notable. 
The  large  amount  of  this  ingredient  in  cereal  straws  is  supposed 
to  be  in  inorganic  form,  and  phosphorus  and  sulphur  have  been 
shown  to  be  present  in  the  stems  of  legumes  and  other  plants  at 
early  stages  of  growth  to  a  large  extent  as  constituents  of  inor- 
ganic compounds.  When  the  plant  is  burned,  sulphur,  phos- 
phorus and  other  acid  forming  elements  which  are  present  in 
organic  compounds,  are  converted  to  acid  radicles.  These  acid 
radicles  combine  with  basic  radicles  simultaneously  formed  from 
calcium,  potassium  and  other  metallic  elements  in  the  plant. 
This  results  in  the  production  of  inorganic  salts,  such  as  potas- 
sium sulphate  and  calcium  phosphate,  in  the  ash.  Any  excess  of 
the  basic  elements  over  the  acid  forming  elements  will  combine 
with  the  carbon  dioxide  present  in  the  air  as  a  result  of  the  process 
of  combustion,  and  will  occur  in  the  ash  as  carbonates.  The 
large  amount  of  potassium  carbonate  in  wood  ashes  is  formed  in 
this  manner.  On  the  other  hand,  any  excess  of  acid  forming 
elements  in  the  plant  will  be  lost  by  volatilization  and  will  fail 
to  appear  in  the  ash.  It  is  thus  evident  that  the  composition  of 
the  ash  gives  little  clue  to  the  previous  status  of  its  constituents 
in  the  plant. 

In  some  cases,  as  with  corn  grain,  where  the  basic  elements  of 
the  plant  are  low,  a  large  part  of  the  sulphur  and  chlorine  may 
be  lost  during  incineration.  The  data  on  page  113  from  Fraps 
illustrates  this  point. 

In  timothy  hay  and  the  tobacco  leaf,  where  these  losses  have 
been  slight,  the  plants  contain  a  high  proportion  of  base  forming 
elements.  In  the  other  plants  tabulated  below  a  lack  of  basic 
constituents,  together  with  a  high  percentage  of  phosphorus,  pre- 
vents complete  retention  of  the  other  acid  forming  elements  dur- 
ing combustion.  With  corn,  Fraps  recovered,  as  an  ash  con- 
stituent, but  one-fiftieth  of  the  total  sulphur  in  that  grain. 

Considerable  knowledge  has  accumulated  as  to  the  status  of 


The  Plant 


113 


these  ash  constituents  in  the  plant.     Their  functions,  however, 
are  in  many  cases  not  clearly  understood. 

Calcium  has  already  been  referred  to  as  a  constituent  of  salts 
of  organic  acids.     It  occurs  widely  distributed  in  this  form.     Al- 
though essential  to  the  plant  and  apparently  playing  an  import- 
Loss  of  Plant  Elements  ~by  Burning 


Sulphur 

Chlorine 

Total 
per  cent 

Per  cent 
determined 
from  ash 

Total 
per  cent 

Per  cent 
determined 
from  ash 

Corn  (seed)  

0.135 
0.186 
0.196 
0.44 
0.20 
0.188 

Trace 
0  03 
0.02 
0.07 
0.17 
0.05 

0.04 
0.008 
0.097 
0.032 

0.888 

Trace 
0.005 
0.005 
0.008 

0.864 

Peas   (seed.)   

Oats   (seed)   •         

Cotton  seed  (  meal  )  

Tobacco  (leaf  )  

Peanuts  (fruit)    

'limothy  (hay)    

ant  part  in  the  chemical  changes  of  living  cells,  its  specific  func- 
tion is  unknown.  In  some  cases  it  appears  to  be  of  advantage  in 
forming  insoluble  salts  of  organic  acids,  such  as  calcium  oxalate, 
CaC204,  thus  preventing  harmful  accumulations  of  free  acids  in 
the  plant.  Loew  is  of  the  opinion  that  calcium-protein  com- 
pounds exist  in  the  organized  parts  of  plant  cells,  from  which 
the  nucleus  and  the  chlorophyll  bodies  are  built  up.  He  at- 
tributes the  characteristic  poisonous  action  of  soluble  oxalates  to 
their  power  of  depriving  these  compounds  of  their  calcium,  con- 
verting it  into  the  insoluble  oxalate.  According  to  this  view, 
calcium  is  particularly  essential  to  the  metabolic  processes  in 
plants. 

Magnesium  exceeds  calcium  in  the  amount  present  in  seeds 
and,  according  to  Loew,  it  is  attended  by  phosphorus  and  favors 
the  assimilation  of  the  latter  element  by  retaining  it  in  the  form 


114  .  Agricultural  Chemistry 

of  soluble  compounds.  In  the  same  manner,  its  abundant  sup- 
ply in  the  seed  favors  easy  assimilation  of  the  reserve  phos- 
phorus of  this  organ  by  the  seedling.  It  is  a  constituent  of 
chlorophyll. 

Potassium  is  of  common  occurrence  as  a  constituent  of  the 
salts  of  organic  acids.  It  has  also  been  known  for  a  long  time 
that  potassium  is  intimately  connected  with  the  formation  of 
starch  and  sugar  by  plants  and  is  uniformly  abundant  in  the 
ash  of  plants  rich  in  these  carbohydrates.  The  presence  of  much 
potassium  has  also  been  repeatedly  observed  in  young  leaves  and 
other  actively  growing  parts  of  plants.  Stoklasa  states  that  it 
is  more  abundant  in  chlorophyll  structures  than  any  other  parts 
of  the  plant.  The  lodging  of  cereal  grain  plants  has  been  at- 
tributed to  lack  of  potassium.  This  theory  is  probably  based 
upon  the  known  stimulating  effect  of  potassium  on  the  forma- 
tion of  cellulose  and  the  simpler  carbohydrates  in  plant  growth, 
since  it  has  been  shown  that  lodging  is  due  in  some  cases  to  lack 
of  cellulose  compounds  in  the  cell  walls  of  the  plant.  Loew 
calls  attention  to  the  efficiency  of  potassium  and  its  compounds 
in  condensing  certain  aldehydes.  He  attributes  to  this  element 
the  function  of  condensation  in  the  formation  of  carbohydrates 
and  proteins. 

Phosphorus  is  an  essential  constituent  of  the  nucleins  and  nu- 
cleo-proteins  around  which  the  activities  of  the  living  plant  cell 
are  centered.  It  is  thus  seen  to  be  an  element  with  complex  and 
most  important  functions.  Phosphorus  is  also  a  constituent  of 
lecithin,  the  chief  function  of  which  has  been  suggested  to  be  that 
of  receiving  fatty  acids  into  its  molecule  and  passing  them  on  in 
soluble  form  to  the  protoplasm  of  the  seedling.  It  would  thus 
serve  as  a  carrier  of  fats,  which  furnish  energy  for  the  first 
growth  of  the  plant. 

Sodium  has  been  shown  to  be  dispensable  with  many  kinds  of 
plants.  There  is  some  evidence  that  sodium  chloride  or  common 
salt  favors  the  action  of  diastase  and  sodium  may  function  in 
this  way  in  the  transformations  of  carbohydrates.  A  consider- 


The  Plant  115 

able  amount  of  work,  especially  an  extended  series  of  plot  ex- 
periments at  the  Rhode  Island  Experiment  Station  with  various 
crops,  has  afforded  evidence  that  sodium  favors  economical 
utilization  of  a  low  potassium  supply,  particularly  when  rela- 
tively more  sodium  enters  the  plant. 

Sulphur  is  a  constituent  of  all  proteins.  It  forms  from  0.4 
to  4.0  per  cent  of  these  compounds.  It  is  a  constituent  of  other 
organic  compounds  known  as  iso-sulpho-cyanates  or  mustard  oils, 
C3H5.N:C:S,  common  to  the  mustard,  turnip  and  other  cruci- 
ferous plants.  The  function  of  these  compounds  is  not  known. 

Iron  is  essential  to  green  plants  and  lack  of  it  produces  a  con- 
dition of  chlorosis,  in  which  the  leaves  become  bleached.  While 
chlorophyll  does  not  contain  iron,  its  action  is  absolutely  depend- 
ent upon  this  element,  small  amounts  of  the  latter  being  ex- 
tremely effective.  Iron  is  a  constituent  of  organic  compounds  in 
the  nuclei  of  plant  cells. 

Chlorine  is  found  to  a  considerable  extent  in  the  ash  of  the 
mangel  and  other  root  crops.  It  exerts  beneficial  action  in  some 
cases  when  applied  as  a  fertilizer  in  the  form  of  the  sodium  salt. 
Nobbe  found  that  buck-wheat  failed  to  develop  beyond  the  flower- 
ing stage  when  lacking  a  supply  of  chlorine,  and  that  great  ac- 
cumulations of  starch  formed  in  parts  of  the  stems  of  the  plant 
under  investigation.  This  has  led  to  the  view  that  chlorine,  in 
the  form  of  the  sodium  salt,  is  essential  to  the  proper  activity  of 
diastase. 

Silicon  is  abundant  in  many  plants,  such  as  the  graminae 
(grass  family,  which  includes  the  cereal  grains),  equisetaceae 
(horse  tails)  and  the  ironwood,  cauto  and  other  trees.  Wicke 
found  that  the  ash  of  the  cauto  tree  contained  96  per  cent  of  sil- 
ica; and  the  ash  of  the  common  scouring  rush  (Equisetum  hye- 
male)  has  been  found  to  contain  97.5  per  cent  of  this  constituent. 
This  element  accumulates  in  the  external  tissues  of  the  plant  as 
a  constituent  of  the  inorganic  compound,  silica.  Oats,  and  corn 
through  three  generations,  have  been  matured  on  traces  of  silicon 
and  this  element  has  been  considered  generally  as  unessential  to 


116  Agricultural  Chemistry 

plants.  There  is  considerable  evidence,  however,  that  this  ele- 
ment favors  economical  utilization  of  small  supplies  of  phospho- 
rus by  plants. 

Of  the  occasional  constituents  of  plant  ash,  manganese  has 
been  found  to  be  an  essential  constituent  of  laccase,  an  enzyme 
in  the  sap  of  the  lac-tree.  It  is  to  this  enzyme  that  the  setting 
of  lacquer  varnish  is  due,  and  its  activity  has  been  found  to  be 
proportional  to  the  amount  of  manganese  present.  The  ash  of 
laccase  contains  as  high  as  2  per  cent  of  manganese. 

Aluminum  occurs  in  some  Lycopodiaceae  (club  mossas)  to  the 
extent  of  22  to  27  per  cent  of  the  ash.  The  recent  work  of  Mose- 
ley  on  the  occurrence  of  aluminum  in  certain  plants  is  of  great 
interest.  He  attributes  to  this  element  the  cause  of  the  disease 
known  as  milk  sickness  or  trembles,  which  may  break  out  oc- 
casionally among  dairy  cattle  and  other  animals.  Moseley  as- 
serts that  animals  contract  the  disease  when  fed  the  white  snake 
root,  which  he  showed  contains  aluminum  phosphate,  A1P04. 
By  the  use  of  this  salt  he  has  reproduced  the  disease  in  smaller 
animals.  The  occurrence  of  the  disease  in  the  southern  states 
has  been  traced  to  the  same  salt,  but  there  occurring  in  the  stems 
of  the  rayless  golden  rod.  In  fact,  Moseley  believes  that  wherever 
trembles  prevails  it  is  caused  by  aluminum  phosphate,  contained 
in  such  plants  as  the  white  snake  root  or  rayless  golden  rod. 

Alpine  cress,  grown  where  the  soil  contained  over  20  per  cent 
of  zinc,  was  found  to  contain  the  following  amounts  of  zinc,  ex- 
pressed as  zinc  oxide  and  in  per  cent  of  the  total  ash : 

Roots   1.66  per  cent 

Stem  3.28 

Leaf    13.12 

Iodine  occurs  in  marine  algae  to  the  extent  of  0.06  per  cent  of 
the  dry  matter.  This  is  of  interest  as  evidence  of  the  assimi- 
lating power  of  the  plant,  since  sea  water  contains  this  element 
to  the  extent  of  only  one  part  in  four  million  or  .0000025  per 
cent.  The  concentration  of  iodine  in  the  plants  is  therefore 
2400  times  as  great  as  in  the  sea  water*. 


The  Plant  117 

Bromine  also  occurs  in  sea  weeds.  Copper,  lead  and  other 
metals  are  sometimes  found  in  plants  growing  upon  soils  which 
contain  such  elements. 

Barium  has  been  found  in  beech  and  birch  trees  and  in  wheat 
grown  upon  barium-containing  soils.  The  presence  of  this  ele- 
ment as  an  ash  constituent  of  certain  leguminous  plants  has  been 
considered  of  practical  concern  to  ranchmen.  It  is  believed  in 
some  instances  to  be  the  active  constituent  of  certain  plants  pro- 
ducing the  loco-disease  in  animals.  These  loco-weeds,  as  they 
are  commonly  called,  have  given  trouble  in  Australia,  and  losses 
to  stockmen  from  this  cause  on  the  United  States  plains  have 
been  heavy.  The  losses  in  Colorado  alone  have  been  estimated 
at  a  million  dollars  yearly.  The  poisonous  effects  upon  live 
stock  of  certain  weeds  of  the  western  plains  appear,  however,  to 
be  due  to  alkaloids. 

From  all  the  evidence  at  hand,  it  appears  -probable  that  all 
the  ash  constituents  normally  present  in  plants  have  some  func- 
tion in  the  chemical  processes  of  plant  growth.  In  this,  connec- 
tion the  compound  phytin  is  of  interest.  This  is  a  complex  salt 
containing  potassium,  calcium  and  magnesium  in  combination 
with  an  organic,  phosphorus-bearing  acid.  It  has  been  isolated 
from  a  number  of  seeds,  including  the  common  cereals,  where  it 
represents  a  concentrated  form  of  storage  of  ash  constituents  for 
the  embryonic  plant.  Phytin  may  influence  the  feeding  value  of 
these  seeds  and  their  products.  It  contains  practically  all  the 
phosphorus,  magnesium  and  potassium  occurring  in  wheat  bran 
and  gives  to  that  dairy  feed  its  laxative  properties. 


CHAPTER  VI 
FARM  MANURE 

For  a  soil  to  possess  fertility,  that  is,  to  be  able  to  properly 
support  the  growth  of  plants,  certain  conditions  are  necessary. 
The  following  may  be  mentioned  as  being  perhaps  the  most  im- 
portant. 

(1)  Its  mechanical  or  physical  condition  must  be  suitable. 

(2)  It  must  contain  sufficient  plant  food  in  a  form  which  is 
readily  available  to  the  crop. 

(3)  It  must  not  contain  any  appreciable  quantity  of  poisonous 
or  injurious  substances. 

(4)  It  must  not  contain  injurious  insects,  fungi  or  other  or- 
ganisms which  are  destructive  to  crops. 

(5)  The  temperature,  sunshine,  rainfall  and  other  climatic 
conditions  must  be  suitable. 

Of  these  the  second  and  third  and  to  some  extent  the  first,  are 
matters  in  which  chemistry  may  be  of  service. 

Every  crop  removed  from  the  soil  robs  it  of  materials  which 
have  been  used  in  building  up  the  plant's  tissues.  Soil  which 
annually  bears  a  crop  must  in  time  become  exhausted  of  its  store 
of  plant  food  and  unfitted  to  bear  further  crops.  Often  one  con- 
stituent of  plant  food  becomes  exhausted  first  and  in  many  cases 
restoration  of  this  constituent  would  renew  the  fertility  for  some 
time  longer.  Substances  which  are  added  to  the  soil  in  order  to 
replace  the  ingredients  which  have  been  removed  by  previous 
crops  are  called  manures. 

All  constituents  of  plants  present  in  a  soil,  except  the  carbon, 
are  diminished  by  the  growth  of  crops  upon  it,  but  the  substances 
which  usually  first  become  deficient  are  combined  nitrogen,  and 
available  phosphorus,  calcium,  potassium  and  possibly  sulphur. 
Consequently  manures  are  valued  according  to  the  quantities  of 


Farm  Manure  119 

these  ingredients  present  in  them,  although  in  many  cases  the 
other  constituents  may  exert  an  important  influence  upon  the 
soil. 

Barnyard  manure.  Of  all  fertilizers,  barnyard  manure  is  the 
oldest  and  still  the  most  popular.  It  consists  of  the  liquid  and 
solid  excreta  of  the  farm  stock,  plus  the  litter  employed.  Early 
Roman  writers  called  attention  to  the  fact  that  the  application 
of  the  excreta  of  farm  animals  resulted  in  increased  production, 
and  from  that  time  to  the  present  the  majority  of  farmers  have 
placed  their  reliance  on  this  class  of  manures  for  maintaining 
the  fertility  of  the  land. 

A  well  kept  manure  heap  may  safely  T)e  taken  as  one  of  the 
surest  indications  of  thrift  and  success  in  farming.  Neglect  of 
this  resource  causes  losses  which,  though  little  appreciated,  are 
vast  in  extent.  "Waste  of  manure  is  either  so  common  as  to 
breed  indifference,  or  so  silent  as  to  escape  notice.  According 
to  recent  statistics  there  are  in  the  United  States  in  round  num- 
bers, 19,500,000  horses,  mules,  etc.,  61,000,000  cattle,  47,000,000 
hogs  and  51,600,000  sheep.  Experiments  indicate  that  if  these 
animals  were  kept  in  stalls  or  pens  throughout  the  year  and  the 
manure  carefully  saved,  the  approximate  value  of  the  fertilizing 
constituents  of  the  manure  produced  by  each  horse  or  mule  an- 
nually would  be  $27,  by  each  head  of  cattle  $20,  by  each  hog  $8, 
and  by  each  sheep  $2.  The  fertilizing  value  of  the  manure  pro- 
duced by  the  different  classes  of  farm  animals  in  the  United 
States,  would  therefore  be  for  horses,  mules,  etc.,  $526,500,000; 
cattle  $1,220,000,000;  hogs,  $376,000,000,  and  sheep,  $103,200,- 
000,  or  a  total  of  $2,225,700,000.  These  estimates  are  based  on 
the  values  usually  assigned  to  phosphoric  acid,  potash  and  nitro- 
gen in  commercial  fertilizers,  and  are  possibly  somewhat  too  high 
from  a  practical  standpoint.  On  the  other  hand  it  must  be  borne 
in  mind  that  no  account  is  taken  of  the  value  of  manure  for  im- 
proving the  mechanical  condition  and  drainage  of  soils,  which  is 
fully  as  important  a  consideration  as  its  direct  fertilizing  value." 

It  is  fair  to  assume  that  at  least  one-third  of  the  value  of  the 
manure  is  annually  lost  through  careless  methods  of  manage- 


120 


Agricultural  Chemistry 


ment.  And  this  estimate  is  conservative.  Even  at  this  figure 
we  have  the  tremendous  sum  of  $750,900,000  as  an  annual  loss 
in  the  United  States.  This  condition  is  the  more  unfortunate 
because  practically  all  of  it  could  be  prevented. 

In  Wisconsin  the  value  of  the  manure  produced  annually  by 
its  1,300,000  milch  cows,  1,100,000  other  cattle,  600,000  horses, 
1,000,000  sheep  and  1,900,000  swine,  based  on  the  above  figures, 
is  approximately  $60,000,000.  And  it  is  also  true  that  as  large 
a  proportion  of  its  valuable  constituents  is  annually  lost  as  in 
any  part  of  the  United  States.  It  is  safe  to  say  that  from  the 
farms  of  "Wisconsin  there  is  an  annual  loss  of  at  least  $20,000,000 
from  the  indifferent  and  careless  management  of  the  manure 
produced. 

Composition  of  manure  from  different  animals.  The  manure 
produced  by  the  various  classes  of  farm  animals  differs  greatly 
in  its  composition  and  physical  properties.  The  following  table 
gives  the  average  composition  of  the  fresh  manure  (including 
solid  and  liquid  excrement)  of  farm  animals.  It  will  be  seen 
from  the  table  that  the  differences  in  composition  are  largely  due 
to  the  variations  in  the  amount  of  water  present : — 

Average  Composition  of  Fresh  Manures 


Animal 

Water 

Nitrogen 

N 

Phos.  Acid 
P208 

Potash 
K20 

Value 
per  ton 

Sheep  

Per  cent 
64  0 

Per  cent 
0.83 

Per  cent 
0.23 

Per  cent 
0.67 

Dollars 
3.39 

Horse  

70.0 

0.58 

0.28 

0.53 

2.55 

Pig  .. 

73.0 

0.45 

0.19 

0.60 

2.14 

Cow  

77.0 

0.44 

0.16 

0.40 

1.89 

Mixed  

75.9 

0.45 

0.21 

0.52 

2.08 

A  ton  of  mixed  manure  of  average  composition  contains  ap- 
proximately 5  pounds  of  phosphoric  acid,  10  pounds  of  nitrogen 
and  10  pounds  of  potash. 

Manures  containing  large  amounts  of  water  are  cold  manures; 


Farm  Manure 


121 


that  is,  they  are  manures  which  heat  slowly  because  the  high 
water  content  checks  fermentations.  Sheep  and  horse  manure 
are  known  as  hot  manures,  due  to  a  lower  water  content  which  is 
favorable  to  a  more  rapid  fermentation. 

Amount  and  value  of  manure  from  different  animals.  It  is 
sometimes  important  for  the  farmer  to  know  the  total  amount 
and  value  of  the  manure  produced  in  a  year  by  the  different  farm 
animals.  In  the  following  table  such  data  are  brought  together, 
with  the  amount  of  manure  calculated  to  the  same  live  weight 
of  the  various  animals. 

Amount  and  Value  of  Manure  per  1000  Ibs.  of  Live  Weight  of 
Different  Animals 


Amount  per  day 

Value  per  day 

Value  per  year 

Sheep  

Pounds 
34.1 

Cents 
7  2 

Dollars 
26  09 

Calves       

67  8 

6  7 

24  45 

Hoes  .  . 

56  2 

10  4 

37  96 

Cows  

74.1 

8  0 

29  27 

Horses  

48.8 

7.6 

27.74 

If  these  figures  are  accepted  as  representing  normal  conditions, 
it,  follows  that  the  sum  of  thirty  dollars  may  be  taken  as  repre- 
senting the  average  value  of  the  fresh  manure  from  each  1000 
pounds  of  live  weight.  The  use  of  this  factor  (thirty  dollars  per 
1000  pounds)  will  enable  the  student  to  calculate  approximately 
what  the  nitrogen,  phosphoric  acid  and  potash  in  the  manure 
produced  on-  his  farm  would  cost,*  if  purchased  in  commercial 
fertilizers,  granting  of  course  that  the  manure  is  so  managed  as 
to  prevent  loss  of  its  valuable  constituents. 


*A11  the  valuations  in  the  calculations  made  are  based  on  15  cents  per 
pound  for  nitrogen  and  5  cents  per  pound  for  phosphoric  acid  and  for 
potash.  This  represents  in  round  numbers  the  market  price  of  these  in- 
gredients in  commercial  fertilizers  at  the  present  time. 


122 


Agricultural  Chemistry 


Factors  which  influence  the  composition  of  manure.  The 
composition  of  the  excrement  varies  greatly,  dependent  on  the 
following  factors: 

(1)  The  character  of  the  ration. 

(2)  Age  and  kind  of  animal. 

(3)  Kind  and  amount  of  absorbents  used. 

Considerable  variation  in  the  composition  of  the  excreta  of 
various  animals  must  necessarily  be  expected. 

Influence  of  the  ration.  The  total  value  of  the  manure  pro- 
duced by  a  given  number  of  animals  is  dependent  on  the  quality 
and  quantity  of  the  feeding  stuffs  used  in  the  ration.  That  the 
different  materials  used  for  feeding  vary  greatly  in  their  fer- 
tilizing value  is  clearly  shown  in  the  following  table,  which  gives 
the  quantity  of  fertilizing  materials  in  one  ton  of  a  few  of  the 
common  feeding  stuffs  and  farm  products.  Additional  figures 
are  to  be  found  in  a  table  of  the  appendix : — 

Pounds  of  Fertilizing  Constituents  in  One  Ton 


Nitrogen 

N 

Phosphoric 
Acid 
P208 

Potash 
KzO 

Value 
per  ton 

Wheat  straw  

Lbs. 
11.8 

Lbs. 
2  4 

Lbs. 
10.2 

Dollars 
2  40 

Corn  Silage     

5.6 

2.2 

7.4 

1.32 

Clover  hay          •  •  •         .... 

41.4 

7.6 

44  0 

8.79 

Wheat  bran  

53.4 

57.8 

32.2 

12.52 

Linseed  meal  

108.6 

33.2 

27.4 

19.22 

Oats  

41.2 

16.4 

12.4 

7.62 

Milk  

10.0 

3.0 

3.0 

1.80 

Butter  

2.0 

1.0 

1.0 

0.40 

Pigs  (live)  

40.0 

17.0 

3.0 

5.00 

The  figures  represent  the  fertilizing  values  of  the  different 
feeds,  provided  they  are  used  directly  as  manures.  It  is  clear 
that  the  richer  the  ration  is  in  nitrogen,  phosphoric  acid  and 
potash,  the  more  valuable  will  be  the  manure  produced  by  the 


Farm  Manure  123 

animal.  It  is  necessary  now  to  inquire  what  proportion  of  the 
fertilizing  content  of  the  food  is  recovered  in  the  excrement. 

Influence  of  age  and  kind  of  animal.  If  a  mature  animal,  as 
a  steer,  for  example,  is  confined  in  such  a  manner  that  all  the 
excrement,  both  liquid  and  solid,  can  be  preserved,  it  will  be 
found  that  all  the  nitrogen,  phosphoric  acid  and  potash  of  the 
food  will  be  contained  in  the  excreta.  This  is  when  the  animal 
is  not  gaining  in  weight.  None  of  these  constituents  will  be 
stored  in  the  tissues,  but  all  are  voided  in  the  dung  and  urine. 
On  the  other  hand,  only  about  half  of  the  total  dry  matter  of  the 
ration  will  be  voided  in  the  excrement,  a  large  part  of  the  other 
half  having  been  given  off  from  the  lungs  as  carbon  dioxide. 
While  the  excreta,  therefore,  contain  only  about  half  of  the  total 
dry  matter  which  was  present  in  the  ration,  they  contain  all  the 
constituents  that  are  generally  considered  of  fertilizing  value. 

With  young  growing  animals,  gaining  in  weight,  the  above 
statement  is  incorrect.  They  retain  a  certain  proportion  of  the 
nitrogen,  potash  and  phosphoric  acid  for  use  in  building  up  their 
bodies.  The  amount  retained  depends  upon  the  age  of  the  ani- 
mal and  its  rate  of  growth.  Experiments  indicate  that  calves 
retain  during  the  first  three  months  of  their  lives  about  one-third 
of  the  fertilizing  value  of  the  food  consumed,  while  the  other 
two-thirds  would  be  found  in  the  excrement.  For  the  first  year 
of  their  existence  they  use  in  growth  about  one-fifth  of  the  nitro- 
gen, phosphoric  acid  and  potash  present  in  the  food  and  as  the 
animal  ages,  the  amount  gradually  diminishes  until  practically 
none  of  these  materials  are  retained.  When  a  mature  animal  is 
fattening  there  is  practically  no  drain  on  the  fertilizing  value  of 
the  feed,  provided  the  gain  is  all  fat.  This  is  due  to  the  fact  that 
fat  contains  only  carbon,  hydrogen  and  oxygen,  and  consequently 
its  production  does  not  remove  any  of  the  fertilizing  constituents. 

The  above  deductions  are  equally  applicable  to  the  other 
classes  of  farm  animals,  such  as  swine,  sheep  and  horses,  and  the 
age  of  the  animal  has  the  same  effect  on  the  value  of  the  manure. 

Influence  of  milk  production.  In  the  case  of  the  cow  another 
factor  is  introduced,  as  a  certain  proportion  of  the  nitrogen, 


124  Agricultural  Chemistry 

phosphoric  acid  and  potash  is  removed  in  the  milk.  One  hun- 
dred pounds  of  milk  contain  on  an  average  about  0.53  pound  of 
nitrogen,  0.19  pound  of  phosphoric  acid  and  0.17  pound  of  pot- 
ash. An  annual  yield  of  five  thousand  pounds,  therefore,  re- 
moves in  the  milk  fertilizing  material  amounting  in  value  to 
$4.90.  If  the  milk  is  sold,  this  is  lost  to  the  farm.  Where  but- 
ter is  made  and  sold,  practically  none  is  carried  away,  as  all  the 
valuable  ingredients  are  left  in  the  skimmed  milk.  The  fertiliz- 
ing value  of  500  pounds  of  butter  amounts  to  about  ten  cents. 
Even  when  the  milk  is  sold,  fully  85  per  cent  of  the  manurial 
value  of  the  food  is  recovered. 

Eighty  per  cent  of  plant  food  recovered  in  manure.  Taking 
into  account  the  relation  between  matured  and  young  stock,  milk- 
producing  and  non-milk-producing  animals,  as  found  on  the 
average  farm,  it  is  conservative  to  assume  that  at  least* 80  per 
cent  of  -all  the  fertilizing  constituents  present  in  the  materials 
fed  on  the  farm,  is  voided  by  the  animals  in  the  solid  and  liquid 
excreta.  This  includes  the  amount  removed  in  the  milk,  that 
retained  by  the  young  animals  during  their  growing  period,  and 
consequently,  the  fertility  removed  from  the  farm  by  the  sale  of 
animals  grown  thereon.  The  fertilizing  value  of  the  excrement 
produced  from  one  ton  of  feeding  material  is  therefore  readily 
ascertained  by  taking  80  per  cent  of  the  fertilizing  value  therein 
stated.  From  this  it  will  readily  be  seen  that  the  composition 
of  the  feeding  stuff  really  determines  the  value  of  the  excrement. 
The  manure  (combined  solid  and  liquid  excrement)  from  one  ton 
of  wheat  straw  would  be  worth  $1.92,  while  that  from  one  ton  of 
corn  meal,  wheat  bran,  or  linseed  meal,  would  be  worth  $5.24. 
$10.01,  and  $15.37  respectively. 

Reference  to  the  table  will  show  that  in  most  cases  the  amount 
of  nitrogen  is  the  factor  determining  the  fertilizing  value  of  a 
feeding  stuff.  This  is  due  to  the  fact  that  nitrogen  is  usually 
present  in  larger  proportion  than  phosphoric  acid  or  potash,  and 
is  much  more  costly  when  purchased.  Wheat  bran  and  linseed 
meal,  however,  are  particularly  rick  in  both  phosphoric  acid  and 
potash. 


Farm  Manure 


.125 


Effect  of  bedding  on  value  of  manure.  Barn  yard  manure, 
as  the  term  is  generally  used,  includes  in  addition  to  the  excreta, 
the  litter  or  bedding  used  to  absorb  the  urine.  The  following 
table  gives  the  composition  of  some  of  the  materials  used  for 
bedding : — 

Fertilizing  Constituents  in  One  Ton  of  Litter 


Nitrogen 

Phosphoric  Acid 

Potash 

Wheat  straw  

Lbs. 
11  8 

Lbs. 
2  4 

Lbs. 
10  2 

Oat  straw    

12  4 

4.0 

24  8 

Clover  straw  

29.4 

8.4 

25.2 

Saw  dust  

4.0 

6.0 

14.0 

Peat  

20.0 

The  richer  the  bedding  the  more  valuable  will  be  the  manure. 
The  materials  commonly  used  for  bedding  are  low  in  the  elements 
of  fertility,  so  that  the  use  of  large  amounts  decreases  the  worth 
per  ton  of  the  manure,  but  in  any  case  sufficient  litter  should  be 
used  to  absorb  all  the  liquid  excrement. 

Calculating  the  amount  of  manure  from  the  ration.  The 
total  weight  of  manure  that  will  be  produced  from  the  material 
fed  an  animal  can  be  calculated  with  considerable  accuracy.  Ex- 
periments have  shown  that  about  50  per  cent  of  the  dry  matter 
present  in  the  ration  is  recovered  in  the  excrement.  The  least 
amount  of  bedding  that  will  absorb  all  urine  excreted  must  con- 
tain dry  matter  equal  to  25  per  cent  of  the  dry  matter  in  the 
feeds  used;  consequently  if  just  enough  bedding  is  used,  the 
manure  (excrement  plus  bedding)  contains  75  per  cent  of  the 
dry  matter  in  the  ration.  Since  mixed  farm  manure  contains  on 
an  average  75  per  cent  of  water,  or  25  per  cent  of  dry  matter,  the 
75  per  cent  of  dry  matter  mentioned  above  must  be  multiplied 
by  four  to  find  the  total  manure.  This  gives  a  result  of  300  per 
cent  of  the  dry  matter  in  the  ration  for  the  weight  of  the  manure. 
In  other  words  if  we  multiply  the  dry  matter  of  the  ration  by 


126  Agricultural  Chemistry 

three,  we  will  have  a  close  approximation  to  the  weight  of  the 
manure  produced.  This  method  of  calculating  holds  true  only 
when  the  theoretical  quantity  of  bedding  has  been  used. 

In  practice  the  farmer  usually  uses  all  the  bedding  material 
he  has  at  hand,  even  if  it  may  exceed  that  necessary  to  absorb  all 
the  urine,  and  such  practice  is  generally  considered  advisable  for 
the  reason  that  such  materials  as  straw  or  shavings  will  decay 
much  more  readily  when  mixed  with  the  excrement  of  animals. 
Where  more  litter  than  the  theoretical  amount  is  used,  the  method 
of  calculation  given  must  be  corrected  by  adding  to  the  total,  the 
weight  of  the  bedding  in  excess  of  25  per  cent  of  the  dry  matter 
of  the  ration. 

Value  of  manure.  The  great  importance  of  barn  yard  manure 
as  a  farm  resource  is  appreciated  to  its  full  extent  by  but  few 
farmers.  A  large  proportion  of  those  engaged  in  agricultural 
pursuits  seem  to  have  little  realization  of  the  immense  loss  in- 
curred through  the  waste  of  this  important  product  of  the  farm. 
They  begrudge  the  time  and  labor  required  to  remove  it  from 
the  barn  and  feeding  lot  and  it  is  not  uncommon  to  see  the  pur- 
chase of  commercial  fertilizers  and  the  waste  of  farm  manure 
going  on  at  the  same  time  and  on  the  same  farm.  Barns  are 
erected  on  steep  hillsides,  or  even  close  to  the  banks  of  running 
streams,  which  practice  insures  a  most  effective  and  wasteful  loss 
of  the  valuable  constituents  of  the  manure  heap. 

In  order  to  fully  emphasize  the  great  value  of  the  manure  pro- 
duced on  the  farm,  figures  are  given  for  the  amount  and  value 
of  the  manure  produced  in  one  year  by  a  herd  of  50  cows  giving 
an  average  individual  yield  of  15  pounds  of  milk  daily.  These 
results  are  largely  taken  from  Vivian's  "First  Principles  of  Soil 
Fertility." 

It  is  assumed  that  the  same  ration  is  fed  throughout  the  year. 
In  actual  practice  the  ration  varies  somewhat  throughout  the 
year,  but  nevertheless  the  good  feeder  aims  to  keep  the  composi- 
tion of  the  ration  very  much  the  same  even  when  various  sources 
of  food  materials  are  drawn  upon. 


Farm  Manure 


127 


The  following  ration  will  be  used  as  a  basis  for  calculation, 
with  the  daily  consumption  for  a  cow  weighing  1,000  pounds  and 
giving  15  pounds  of  milk ;  10  pounds  of  a  mixture  of  one-third 
each  of  corn  meal,  ground  oats  and  bran;  35  pounds  of  corn 
silage;  15  pounds  of  clover  hay  (medium  red).  This  is  a  good 
practical  ration  and  conforms  well  with  the  best  feeding  stand- 
ards. It  will  be  assumed  that  just  the  amount  of  wheat  straw 
which  would  theoretically  be  necessary  to  absorb  the  liquid  ex- 
crement is  used  as  bedding.  Allowance  for  milk  production  is 
of  course  made  by  using  the  factor  of  80  per  cent  as  the  basis 
for  calculating  the  amounts  of  fertilizing  material  recovered  in 
the  excrement  from  the  total  contained  in  the  feeds. 

Fertilizing  Constituents  of  the  Manure 


Nitrogen 

Phosphoric  Acid 

Potash 

In  excrement  

Lbs. 

8958  47 

Lbs. 
3483  50 

Lbs. 

7982.77 

In  bedding  

742  61 

340  .  22 

974.28 

Totals  

9701  08 

3823.72 

8957  05 

The  prices  paid  for  fertilizing  materials  at  the  present  time 
are  15  cents  per  pound  for  nitrogen  and  5  cents  each  for  phos- 
phoric acid  and  potash.  These  prices  hold  only  when  raw  ma- 
terials are  bought,  and  much  higher  prices  are  paid  for  mixed 
fertilizers.  From  these  prices  is  calculated  the  total  value  of 
the  manure  produced  by  50  cows  in  one  year: 

Value  of  Manure  for  Fifty  Cows 

Value  of  nitrogen   11455.18 

Value  of  phosphoric  acid   191.19 

Value  of  potash   447.85 


Total  value  of  manure $2094.22 


128  Agricultural  Chemistry 

This  means  that  the  fresh  manure  from  50  cows  contains 
amounts  of  nitrogen,  phosphoric  acid  and  potash  that  would  cost 
the  farmer  at  least  $2094.22  if  purchased  in  commercial  fertil- 
izers. The  amount  of  manure  produced  would  weigh  811.9 
tons,  giving  a  value  of  $2.58  for  each  ton.  How  near  the  actual 
agricultural  value  of  the  manure  will  approach  the  trade  value 
will  depend  upon  a  number  of  conditions,  such  as  crop  to  be 
fed,  physical  condition  of  the  soil,  climate,  and  especially  the 
management  of  the  manure  itself.  The  same  statement  applies 
to  commercial  fertilizers,  the  trade  price  being  no  indication  of 
the  agricultural  value  of  the  material,  and  the  farmer  who  profits 
most  from  the  use  of  commercial  fertilizers  is  also  the  one  to  be 
best  repaid  for  the  use  of  barn  yard  manure.  In  experiments 
conducted  at  the  Ohio  Experiment  Station  and  covering  a  period 
of  fourteen  years,  it  was  found  that  the  average  value  of  the  in- 
crease of  crop  produced  ~by  one  ton  of  fresh  manure  amounted  to 
$3.31.  If  50  cents  per  ton  be  allowed,  as  the  cost  of  applying 
the  manure  to  the  field,  there  still  remains  a  substantial  profit, 
as  the  result  of  the  application. 

How  to  increase  the  value  of  manure.  "Where  a  system  of 
animal  husbandry  is  practiced,  the  farmer  will  find  that  the  most 
economical  way  to  increase  the  plant  food  for  the  farm  is  by 
purchasing  feeding  stuffs  rich  in  fertilizing  constituents,  feeding 
them  to  the  animals  and  using  the  manure  as  a  fertilizer.  In 
a  system  of  grain  farming  he  will,  of  course,  be  obliged  to  supply 
his  deficiency  in  plant  food  by  direct  purchase  of  the  needed 
elements  in  the  form  of  commercial  fertilizers.  The  successful 
stockman  finds' it  profitable  to  reinforce  the  feeds  raised  on  the 
farm  with  one  or  more  of  the  various  mill  and  other  by-products 
that  are  sold  as  cattle  feeds.  A  farmer  who  buys  large  quan- 
tities of  concentrates  is  increasing  the  fertility  of  his  land  pro- 
vided he  is  taking  proper  care  of  the  manure.  At  the  University 
Farm  there  is  an  annual  gain  in  fertilizer  elements  from  pur- 
chased feeding  stuffs  over  the  losses  sustained  by  the  sale  of  ani- 
mals and  animal  products. 


Farm  Manure  129 

In  purchasing  feeding  stuffs,  one  should  always  consider  their 
fertilizing  value,  as  well  as  their  feeding  value,  for,  while  the 
substance  is  bought  primarily  to  feed,  it  is  sometimes  possible  to 
buy  different  materials  which  will  serve  practically  the  same  as 
feeds  and  yet  vary  greatly  in  their  value  as  fertilizers.  It  is  in- 
deed often  sane  practice  to  sell  some  of  the  products  produced 
on  the  farm  and  with  the  money  thus  obtained  purchase  other 
feeding  materials.  There  is  scarcely  a  farm  on  which  such  an 
exchange  could  not  be  made  to  advantage. 

The  following  example  will  illustrate  more  clearly  what  is 
meant.  At  the  time  of  writing  it  was  possible  to  buy  on  the 
local  market  6.4  tons  of  clover  hay  for  the  price  of  5  tons  of 
timothy  hay,  and  5  tons  of  corn  could  have  been  exchanged  for 
4.6  tons  of  wheat  bran.  Calculating  the  value  of  fertilizing 
materials  in  the  manner  already  described,  the  results  are  as 
follows : 

Fertilizing  value  of  6.4  tons  of  clover $43.58 

Fertilizing  value  of  4.6  tons  of  bran  57.54 


Total $101.12 

Fertilizing  value  of  5  tons  of  timothy $26.05 

Fertilizing  value  of  5  tons  of  corn 32.80 


Total $58.85 

Gain  due   to   exchange    42.27 

By  a  simple  exchange  of  products  without  any  cash  outlay  the 
fertilizing  value  of  the  ration  has  been  increased  $42.27  and  con- 
sequently the  manure  produced  would  have  been  worth  $33.81 
more  than  that  resulting  from  the  use  of  corn  and  timothy  hay. 
This  example  is  offered  merely  as  a  suggestion,  which  may  be 
made  of  considerable  practical  value,  dependent  on  the  market 
prices  of  the  various  feeds. 

In  the  above  example  the  actual  feeding  value  has  been  in- 
creased in  the  exchange  due  to  the  increase  in  protein  in  both 
clover  and'  bran,  with  no  decrease  but  rather  an  actual  gain  in 
the  dry  matter  purchased. 


130  Agricultural  Chemistry 

Reinforcing  the  manure  with  commercial  plant  food.  In 
systems  of  animal  husbandry  or  in  systems  of  mixed  farming  it 
is  becoming  common  practice  to  reinforce  the  manure  with  com- 
mercial plant  food.  Experiments,  continuing  over  many  years 
at  the  Ohio  Experiment  Station,  have  shown  for  that  soil  prof- 
itable increase  in  crops  resulting  where  the  manure  was  rein- 
forced with  either  kainit,  gypsum,  floats  or  acid  phosphate  (see 
next  chapter  for  description  of  these  substances). 

These  materials  were  applied  at  the  rate  of  40  pounds  per  ton 
of  manure.  In  these  experiments  the  greatest  net  return  was 
from  the  application  of  acid  phosphate,  although  floats  gave 
nearly  as  high  a  value  and  enriched  the  soil  with  more  phos- 
phorus in  the  amount  applied  than  did  the  same  weight  of  acid 
phosphate.  The  value  in  crop  increase  per  ton  of  stable  manure 
alone  was  $3.31 ;  the  net  value  in  crop  from  stable  manure  and 
kainit  was  $3.71 ;  stable  manure  and  gypsum  $3.56 ;  stable  manure 
and  floats  $4.49 ;  stable  manure  and  acid  phosphate  $4.82. 

Probably  for  mast  soils  the  reinforcement  of  manure,  for 
greatest  profit,  should  be  with  floats,  which  furnishes  additional 
phosphorus,  and  with  gypsum,  which  furnish  an  additional  sup- 
ply of  sulphur.  These  materials,  mixed  with  the  manure  at  the 
rate  of  40  pounds  each  per  ton,  will  furnish  another  method,  in 
systems  of  animal  husbandry  and  mixed  farming,  of  maintain- 
ing and  increasing  the  supply  of  these  two  critical  plant  food 
elements  in  the  soil. 

Losses  in  manure.  Barn  yard  manure  is  a  perishable  prod- 
uct and  must  be  handled  with  intelligence  to  obtain  its  maximum 
value.  Doubtless  as  manure  is  handled  on  the  majority  of  farms, 
only  one-half  of  its  worth  is  realized.  The  greatest  loss  is  through 
the  waste  of  the  liquid  excrement  by  the  use  of  insufficient  bed- 
ding to  absorb  it.  The  boring  of  holes  in  the  floor  for  the  express 
purpose  of  allowing  the  urine  to  run  off  as  rapidly  as  possible  is 
by  no  means  an  uncommon  practice.  The  table  on  the  next  page 
gives  the  composition  of  the  solid  and  liquid  excrement. 


Farm  Manure 


131 


Pound  for  pound  the  liquid  excrement  is  more  valuable  than 
the  solid,  except  in  the  case  of  swine.  It  is  perfectly  safe  to  say 
that  of  the  total  fertilizing  material  in  the  manure,  two-thirds  of 
the  nitrogen,  four-fifths  of  the  potash,  and  practically  none  of 

Percentage  of  Fertilizing  Constituents  in  Solid  and  Liquid  Excrements 


Nitrogen 

Phosphoric  Acid 

Soda  and  Potash 

Solid 

Liquid 

Solid 

Liquid 

Solid 

Liquid 

Horses  

Per  cent 
.50 
.30 
.60 

.75 

Per  cent 
1.20 

o.'so 

0.30 
1.40 

.  er  cent 
0.35 
0.25 
0.45 
0.60 

Per  cent 
Trace 
Trace 
0.12 
0.05 

Per  cent 
0.30 
0.10 
0.50 
0.30 

Per  cent 
1.60 

1.40 
0.2U 
2.00 

Cows  

Swine  

Sheep  

the  phosphoric  acid,  are  found  in  the  urine.  It  is  apparent  that 
somewhat  over  half  of  the  total  value  of  the  manure  is  in  the 
urine.  Had  the  liquid  portion  of  the  manure  been  allowed  to 
run  away,  the  value  of  the  excrement  as  calculated  in  the  ex- 
ample given  above  would  have  been  less  than  $1000  instead  of 
$2049. 

Another  fact  of  great  importance  in  this  connection  is  that  the 
plant  food  in  the  urine  is  in  a  form  that  is  soluble  in  water  and 
consequently  more  available  to  plants  than  that  in  the  solid  dung. 
This  is  particularly  true  of  the  nitrogen.  The  solid  excrement 
consists  in  part  of  the  undigested  portion  of  the  food,  and  before 
its  nitrogen  can  become  available  to  plants,  it  must  undergo  de- 
composition and  decay. 

The  difference  in  value  of  the  solid  and  liquid  excrement  is 
well  brought  out  in  the  following  experiment  from  the  New  Jer- 
sey Experiment  Station.  Two  plots  were  treated  with  manure, 
the  one  receiving  only  solid  excrement,  while  on  the  other  the 
mixed  solid  and  liquid  excrement  was  used.  Each  plot  received 


132 


Agricultural  Chemistry 


enough  of  the  manure  to  supply  equal  quantities  of  nitrogen. 
The  results  are  stated  in  percentage  of  gain  over  a  check  plot 
that  received  no  manure. 

Percentage  of  Gain  in  Yield  from  Manure 


Solid  excrement  only 

Solid  and  liquid 
excrement 

First  vear  

15.2 

52.7 

Second  vear  .                    .... 

69  7 

116  9 

Third  year  

47  9 

80.6 

Average  

44.3 

83.4 

The  table  clearly  shows  that  the  yield  from  the  same  amount 
of  nitrogen  was  very  much  larger  from  the  mixed  manure  than 
from  the  solid  excrement  alone.  The  experiment  also  indicates 
that  the  nitrogen  in  the  liquid  excrement  was  much  more  readily 
utilized  by  the  plant  than  that  in  the  solid  excrement. 

Manure  is  never  so  valuable  as  wlien  fresh;  and  the  very  best 
methods  of  handling  and  care,  if  the  manure  must  be  stored,  can- 
not prevent  some  loss  of  the  valuable  constituents.  For  this 
reason,  it  is  advisable  when  possible,  to  apply  manure  to  the 
field  as  fast  as  it  is  made. 

Losses  in  manure  from  leaching.  In  addition  to  the  great 
losses  due  to  improper  absorption  of  the  urine,  the  manure  suffers 
heavily  from  leaching  by  rains.  This  is  probably  the  greatest 
source  of  loss.  It  is  often  allowed  to  lie  for  months  in  the  open 
barn  yard,  or  better,  directly  under  the  eaves  of  the  barn,  where 
the  leaching  and  washing  processes  are  more  complete.  Even 
after  plenty  of  litter  has  been  used  and  all  urine  absorbed,  it  is 
not  uncommon  to  see  it  placed  where  it  is  directly  exposed  to 
the  continuous  action  of  the  elements. 

At  the  New  Jersey  Experiment  Station  four  samples  of  ma- 
nure were  exposed  to  the  weather  for  varying  lengths  of  time  and 


Farm  Manure 


133 


the  losses  determined.     The  results  are  given  in  the  following 
table : 

Losses  in  Manure  from  Leaching 


Period  in  days 

Nitrogen 

Phosphoric  Acid 

Potas  h 

131  

Per  cent 
57.0 

Per  cent 
62  0 

Per  cent 
72.0 

70.. 

44  0 

1(5.0 

28.0 

76  

39.0 

63.0 

5K.Q 

50  

69.0 

59.0 

72.0 

Average  

51  0 

51.1 

61.1 

The  average  loss  amounted  to  more  than  50  per  cent  of  the 
value  of  the  manure  during  rather  short  periods.  It  is  very 
common,  if  not  the  rule,  to  find  manure  exposed  on  many  farms 
for  longer  periods  than  here  shown.  The  aggregate  loss  of  the 
plant  food  of  the  country  by  such  exposure  is  appalling.  Ex- 
periments at  the  Cornell  Experiment  Station  with  manure  ex- 
posed to  the  weather  for  a  period  of  five  months  (April  to 
September)  gave  the  following  data: — 


Value  at  begin- 
ing  per  ton 

Loss  per  ton 

Loss  per  cent 

Horse  manure  

$2  80 

$1  74 

62.0 

Cow  manure    

2.29 

0.69 

30.0 

It  is  necessary  to  state  that  the  losses  will  vary  with  climatic 
conditions.  During  heavy  rain  in  warm  weather,  the  losses  ivill 
be  heavier  than  in  dry  or  cold  weather. 

Losses  from  solid  excrement  by  leaching.  Not  only  is  the 
liquid  portion  of  the  excreta  of  the  animal  lost  by  exposure  to 
leaching,  but  in  addition,  the  solid  excrement  suffers  loss.  A 


134 


Agricultural  Chemistry 


considerable  portion  of  both  the  phosphoric  acid  and  potash 
eliminated  through  the  intestine  is  in  a  soluble  form,  and  the 


Manure  leaching.     How  the  manure  in  America  is  wasted. 

chemical  changes  constantly  going  on  in  a  manure  pile  are  mak- 
ing soluble  the  insoluble  nitrogenous  portions  of  the  dung. 

The  following  table  illustrates  the  losses  which  may  occur  when 
the  solid  excrement  alone  is  exposed  for  varying  lengths  of  time. 

Losses  in  Solid  Excrement  from  Leaching 


Period  in  days 

Nitrogen 

Phosphoric  Acid 

Potash 

13!  

Per  cent 
46-0 

Per  cent 
72  0 

Per  cent 
80.0 

70  

34.0 

27.0 

10.0 

7(5  

25  0 

54  0 

48.0 

50  

45.0 

42.0 

42.0 

Average  

37.6 

51.9 

47.1 

Farm  Manure 


135 


In  addition  to  the  actual  losses  taking  place,  the  character  of 
the  material  lost  is  of  considerable  importance.  The  nitrogen  in 
the  portion  removed  by  leaching,  is  more  valuable,  pound  for 
pound,  than  that  remaining,  because  it  is  in  a  form  more  im- 
mediately available  to  the  crop. 

In  an  experiment  at  the  New  Jersey  Experiment  Station  two 
plots  were  treated  with  quantities  of  fresh  and  leached  manure, 
both  containing  exactly  the  same  amounts  of  nitrogen.  The  re- 
sults are  tabulated  below  and  are  stated  in  percentage  of  gain 
over  a  plot  receiving  no  manure. 

Per  cent  of  Gain  in  Yield  from  Manure 


Fresh  Manure 

Leached  Manure 

First  year  

52.7 

41.5 

Second  vear  

108.4 

96.8 

Third  vear      

187.5 

89.6 

Average  

116.9 

76.0 

The  common  practice  of  open  yard  feeding,  where  the  manure 
produced  during  the  winter  is  spread  over  a  considerable  area 
and  often  allowed  to  remain  until  late  spring,  or  even  into  the 
fall,  is  most  wasteful  of  the  fertilizing  material  it  contains.  It  is 
safe  to  say  that  at  least  one-half  of  the  fertilizing  value  of  the 
manure  is  lost  by  such  practice.  This  method  of  feeding  is  ex- 
tremely common  and  in  the  corn  belt  of  this  country  it  is  not 
unusual  to  see  a  large  feeding  yard  covered  to  a  considerable 
depth  with  manure,  under  ideal  conditions  for  maximum  leach- 
ing. 

Losses  by  fermentation.  Manure  is  very  easily  decomposed 
and  the  losses  resulting  from  such  decomposition  fall  entirely  on 
the  most  valuable  constituent  of  the  manure,  the  nitrogen. 
Through  the  process  of  fermentation  no  potash  or  phosphoric 


136  Agricultural  Chemistry 

acid  is  lost.  These  manurial  ingredients  are  wasted  only  through 
leaching. 

The  first  evidence  of  fermentation  is  the  odor  of  ammonia. 
This  is  noticeable  in  the  barn,  especially  if  it  has  been  closed 
during  the  night.  It  is  due  to  the  rapid  decomposition  of  urea, 
the  principal  nitrogenous  body  of  the  urine  according  to  the  fol- 
lowing equation : 

CO(NH2)2+2H2O=2NH3+C02+H20 
urea  ammonia 

Ammonia  contains  nitrogen  and  when  its  presence  is  noticed,  it 
is  evident  that  nitrogen  is  escaping  into  the  air.  It  is  impos- 
sible to  entirely  prevent  the  formation  of  ammonia  from  the 
urea,  but  it  is  possible  to  greatly  reduce  its  loss  by  providing 
plenty  of  absorbing  material  and  keeping  the  manure  moist. 

The  fermentation  of  manure  is  due  to  different  kinds  of  bac- 
teria. Some  of  these  can  exist  only  in  the  presence  of  air  and 
are  called  "aerobic,"  while  others  do  not  require  free  air  and 
are  classified  as  "anaerobic."  The  aerobic  organisms  are  re- 
sponsible for  the  hot  fermentation  which  is  the  cause  of  great 
loss  of  value  in  manure.  It  is  well  known  that  when  manure  is 
thrown  into  loose  heaps  and  contains  a  large  proportion  of  horse 
or  sheep  excrement  it  soon  becomes  very  hot  and  dry,  in  fact,  hot 
enough  to  steam,  and  the  temperature  may  reach  175°  Fahr. 
In  this  condition  the  common  fire  fanging,  or  burning  white  in 
spots,  takes  place,  and  heavy  losses  of  nitrogen  are  sure  to  oc- 
cur. Experiments  have  shown  losses  of  from  30  to  80  per  cent 
of  the  nitrogen.  In  extreme  cases  of  fire-fanging  all  the  nitro- 
gen will  be  lost.  Other  losses  fall  on  the  decomposition  of  the 
cellulose  and  carbohydrates  of  the  litter  and  fecal  residues. 
These  fermentations  give  rise  to  the  production  of  such  gases  as 
methane,  hydrogen,  and  carbon  dioxide  thus: — 
2CflH1008+302=8C08+4CH4+2Ha 

cellulose  methane 

If  the  manure  heap  is  so  compact  that  the  air  cannot  penetrate 
it,  the  aerobic  bacteria  are  unable  to  live,  and  hence  hot  fermen- 


Farm  Manure  137 

tation  is  prevented.  Where  aerobic  bacteria  are  active  the  solu- 
ble forms  of  nitrogen  in  the  manure  are  partly  converted  into 
nitrates  and  these  in  turn  may  be  attacked  by  certain  anaerobic 
bacteria  called  denitrifiers,  which  liberate  elemental  or  free  ni- 
trogen from  such  compounds.  This  is  an  additional  reason  for 
checking,  so  far  as  possible,  all  aerobic  fermentations.  The 
presence  of  large  quantities  of  water  in  the  manure  heap  holds 
the  temperature  down,  displaces  the  air  and  in  this  way  checks 
aerobic  fermentations.  For  this  reason,  the  moist  cow  and  pig 
excrements  are  not  so  subject  to  hot  fermentation  as  that  of  the 
horse  or  sheep.  This  explains  the  sound  practice  of  mixing  the 
manure  from  the  various  classes  of  farm  animals,  when  it  is 
necessary  that  it  be  stored. 

"When  the  manure  is  in  a  compact  mass  and  moist  the  fer- 
mentations that  take  place  are  due  to  anaerobic  bacteria.  These 
fermentations  convert  the  insoluble  plant  food  in  the  excrement 
into  soluble  forms,  with  little  loss  of  the  fertilizing  constituents. 
There  is  however  a  constant  decomposition  of  materials  with  the 
evolution  of  gases  containing  carbon  and  hydrogen,  and  a  con- 
sequent loss  of  organic  matter  during  the  anaerobic  rotting 
process  thus: — 

C6H1200=2H2+2C02+C4H802 
sugar  butyric  acid 

or 

2C6H1005=5C02+5CH4+2C 

cellulose  methane 

In  these  reactions  the  by-products  are  such  gases  as  carbon  di- 
oxide, hydrogen,  and  methane.  It  should  be  noted  that  the 
anaerobic  fermentation  does  not  entail  an  escape  of  gaseous  ni- 
trogen. Under  the  best  conditions  of  care,  it  is  impossible  to 
entirely  prevent  losses  in  stored  manure,  although  if  properly 
preserved  it  may  be  reduced  to  about  10  per  cent  of  the  nitrogen 
and  none  of  the  other  two  fertilizing  constituents.  The  am- 
monium carbonate  formed  from  the  urea  is  itself  subject  to 
change  and  even  loss  by  other  actions  than  evaporation.  There 


138  Agricultural  Chemistry 

are  always  present  in  the  manure  heap  various  bacteria  which 
can  oxidize  ammonia  into  free  nitrogen  gas  and  water,  thus : 

4NH3+302=2N2+6H20. 

In  consequence  of  the  above  change,  manure  which  is  allowed  to 
lie  about  loosely  grows  poor  in  nitrogen  from  this  cause  as  well 
as  through  the  volatilization  of  ammonia. 

Preservation  of  manure.  Saving  the  urine.  From  all  that 
has  been  said  it  must  appear  perfectly  plain  that  one  of  the 
greatest  losses  suffered  by  the  farm  is  through  failure  to  save  the 
liquid  excrement  of  the  animal.  To  insure  against  such  loss, 
that  part  of  the  barn  floor  on  which  the  excrement  falls  must 
be  so  tight  that  none  of  the  liquid  can  drain  away. 

The  trough  behind  the  animals  should  be  made  absolutely  tight 
by  the  use  of  pitch,  cement,  or  some  other  material  that  is  im- 
pervious to  water.  Besides  this  precaution,  enough  litter  should 
be  used  so  that  all  urine  is  absorbed  and  none  runs  away  by 
dripping,  when  the  manure  is  removed  from  the  barn.  It  is 
often  of  the  greatest  advantage  to  finely  cut  the  bedding  ma- 
terial. This  increases  its  absorbing  capacity,  and  facilitates 
handling  the  manure.  Straw  cut  in  one  inch  lengths,  for  ex- 
ample, will  absorb  about  three  times  as  much  urine  as  long 
straw. 

Stockmen  who  have  practiced  cutting  the  bedding  assert  that 
the  great  ease  with  which  the  manure  will  be  removed  and  spread 
will  repay  the  cost  and  trouble,  to  say  nothing  of  the  saving  of 
bedding  materials. 

Use  of  preservatives.  As  has  been  previously  explained,  the 
urine  of  all  farm  animals  contains  its  nitrogen  principally  in  the 
compound  known  as  urea.  This  body  is  rapidly  and  readily  de- 
composed by  ferments  and  changes  into  ammonium  carbonate. 
This  latter  substance  is  volatile  and  passes  off  into  the  air,  where 
it  can  be  detected  by  the  sense  of  smell,  that  is,  by  the  odor  of 
ammonia.  The  dry  manures,  as  those  of  the  horse  and  sheep,  are 
particularly  subject  to  this  loss  of  nitrogen,  which  is  contained 
in  the  escaping  ammonia.  Many  from  the  farm  have  suffered 


Farm  Manure  139 

with  "smarting  eyes"  when  removing  the  accumulated  manure 
from  the  horse  stable.  This  is  due  to  the  ammonia  and  can  be 
prevented  partly  by  the  use  of  land  plaster  or  gypsum.  How- 
ever, to  accomplish  this  completely  excessive  quantities  of  gyp- 
sum must  be  used  as  the  reaction  is  a  reversible  one. 

(NH4)  2C03+CaS04=CaC08+  (NHJ  2S04 

This  fixes  the  ammonia  in  part,  by  forming  ammonium  sulphate,, 
which  is  a  non- volatile  body.  In  using  gypsum  scatter  it  on  the 
floor  immediately  after  the  barn  has  been  cleaned  and  before  the 
fresh  bedding  has  been  spread.  From  one-half  to  one  pound  per 
animal  each  day  is  used  in  common  practice.  It  is  not  impossible 
that  part  of  the  beneficial  results  obtained  by  adding  gypsum 
in  the  manure  and  to  the  land  comes  from  the  additional  supply 
of  sulphur. 

Other  preservatives,  as  kainite,  muriate  of  potash  and  acid 
phosphate,  are  often  recommended  as  preservatives  for  manure 
and  to  prevent  the  loss  of  nitrogen.  They  are  reported  to  be 
injurious  to  the  hoofs  of  animals  and  when  used  should  be  scat- 
tered on  the  floor  and  carefully  covered  with  bedding.  There  is 
much  difference  of  opinion  as  to  their  merits  as  preservatives, 
but  unquestionably  they  all  can  effect  a  partial  retention  of 
escaping  ammonia  and  thus  act  as  barn-sweeteners.  They  will 
also  serve  the  additional  function  of  reinforcing  the  manure  with 
fertilizing  materials.  They  may  be  used  in  the  same  quantity  as 
recommended  for  gypsum.  Dry  earth  has  been  recommended 
for  the  same  purpose  and  is  especially  useful  in  this  regard,  par- 
ticularly where  it  contains  a  large  amount  of  humus.  In  some 
parts  of  the  country  dry  peat  or  muck  soil  is  in  use  in  the  stable 
in  connection  with  the  bedding.  It  should  never  be  used  in  quan- 
tities sufficient  to  make  the  manure  dry,  as  this  would  result  in 
still  greater  nitrogen  losses. 

Haul  the  manure  when  fresh.  Manure  is  never  so  valuable 
as  when  perfectly  fresh,  for  it  is  impossible  under  the  best  sys- 
tem of  management  to  prevent  all  loss  of  its  fertilizing  ingre- 
dients. For  this  reason  it  is  recommended  that  wherever  pos- 


140 


Agricultural  Chemistry 


sible,  the  manure  should  be  hauled  directly  to  the  field  and 
spread.  It  is  the  most  economical  of  time  and  labor,  as  it  in- 
volves handling  but  once.  "While  it  is  true  that  it  will  be  leached 
by  the  rain,  nevertheless,  the  soluble  portion  will  be  carried  into 
the  soil,  where  it  is  desired  to  have  it.  When  spread  in  a  thin 
layer,  it  will  not  heat,  so  there  will  ~be  no  loss  from  hot  fermen- 
tation ;  and  where  manure  simply  dries  out  when  spread  on  the 
ground,  there  is  no  loss  of  valuable  constituents. 


Wherever  possible,  haul  and  spread  the  manure  daily  as  produced. 

Storing  manure.  When  it  is  impossible  to  remove  the  manure 
directly  to  the  field,  due  to  weather  conditions  or  lack  of  avail- 
able fields,  the  problem  of  properly  storing  it  will  present  itself. 
From  what  has  already  been  said,  it  is  apparent  that  the  two  in- 
jurious processes,  namely  leaching  and  hot  fermentation,  must 
be  prevented.  The  effect  of  leaching  may  be  prevented  in  two 
ways;  either  by  providing  water  tight  receptacles  so  that  the 
liquid  cannot  run  away,  or  by  keeping  the  manure  under  cover 
so  as  to  protect  it  from  the  rains.  The  first  method  is  in  general 
use  in  Europe,  where  pits  or  cisterns  of  cement  or  other  imper- 
vious material  are  built  and  in  which  the  manure  is  stored.  Some- 
times a  pump  is  provided,  whereby  the  liquid  portion  is  again 


Farm,  Manure 


141 


pumped  over  the  more  solid  portion,  keeping  it  moist  and  fur- 
thering decay  with  minimum  loss.  This  process  makes  excellent 
manure  but  requires  time  and  labor.  The  more  economical  way 
for  the  American  farmer  to  prevent  leaching,  when  manure  must 
be  stored,  is  to  keep  it  under  cover.  A  cheap  lean-to  or  shed  is 
all  that  is  needed.  Where  it  is  possible,  a  water-tight  floor 
should  be  provided. 

Where  neither  cement  cistern  nor  covered  shed  is  available, 
and  it  becomes  absolutely  necessary  to  store  the  manure,  the  heap 


When  the  manure  must  be  stored  and  there  is  no  cover,  build  the  pile 
as  shown   above. 

should  be  made  so  high  and  compact  that  the  hardest  rain  will 
not  soak  through.  The  sides  should  be  perpendicular  and  the 
top  dipped  toward  the  center.  It  is  advantageous  to  have  the 
manure  saturated  with  water,  but  large  losses  of  plant  food  would 
result  should  the  water  drain  away  from  the  heap. 

Hot  fermentation  can  be  controlled  by  keeping  the  manure  pile 


142  Agricultural  Chemistry 

moist  and  compact.  These  two  conditions  exclude  the  air  from 
the  pile  and  prevent  the  action  of  that  class  of  bacteria  which 
causes  hot  fermentation  and  in  addition,  require  free  oxygen  for 
their  activity.  When  the  heap  shows  a  tendency  to  dry  out, 
water  should  be  added  and  each  daily  addition  of  manure  to  the 
pile  firmly  packed  into  place.  This  allows  decomposition  to  con- 
tinue, liberating  the  more  insoluble  plant  food  from  organic  con- 
stituents of  the  manure  and  greatly  improving  its  mechanical 
condition.  Mixing  the  manure  from  the  various  farm  animals 
is  the  very  ~best  practice.  The  drier  horse  and  sheep  manure  are 
checked  in  their  fermentation  by  the  more  moist  pig  and  cow 
excrements.  When  it  becomes  necessary  to  store  the  manure  for 
.some  time,  it  is  recommended  to  cover  the  heap  with  an  inch  or 
two  of  earth.  This  prevents  the  escape  of  any  ammonia  that  may 
be  formed. 

Covered  sheds  save  manure.  Professor  Roberts,  formerly  of 
Cornell  University,  was  a  strong  advocate  of  covered  barn  yards 
for  the  conservation  of  manure.  They  are  simply  sheds,  with 
good  roofs,  with  or  without  sides  and  large  enough  to  allow  the 
cattle  to  move  about  freely.  The  bottom  is  made  tight  by  pud- 
dling clay  or  using  cement.  The  manure,  as  removed  from  the 
barn,  is  spread  about  and  sufficient  bedding  distributed  over  the 
surface  to  insure  cleanliness.  The  animals  trample  the  accumu- 
lating manure  into  a  compact  mass  and  keep  it  moist  by  their 
liquid  excrement.  This  insures  an  excellent  manure,  with  but 
slight  losses  of  plant  food.  In  addition,  it  affords  exercise  and 
a  healthful  environment  for  the  animals  in  severe  weather.  The 
plan  has  been  tried  by  many  dairymen  and  is  generally  consid- 
ered very  satisfactory.  It  is  said  that  the  cows  keep  cleaner  than 
when  stabled  and  that  the  milking  barn  is  in  a  more  sanitary 
condition. 

The  throwing  of  cattle  and  horse  manure  into  basement  rooms 
to  be  worked  over  by  the  hogs,  is  from  the  standpoint  of  the  con- 
servation of  plant  food,  an  economical  process.  By  tramping 
and  working  over  the  manure,  and  by  adding  their  own  excre- 
ment, the  mass  is  kept  moist  and  fermentation  controlled. 


Farm  Manure  143 

Deep  stall  manure.  In  some  parts  of  Europe  the  deep  stall 
method  of  saving  manure  is  in  vogue.  It  consists  in  excavating 
the  stalls  where  the  cattle  stand  to  some  depth  below  the  barn 
floor  level.  Every  day  the  manure  is  spread  evenly  over  the  stall 
and  fresh  bedding  added.  The  excrement  and  bedding  are  firmly 
packed  by  the  feet  of  the  animal  and  allowed  to  remain  through- 
out the  winter.  The  manure  produced  is  of  excellent  quality, 
but  for  sanitary  reasons  the  practice  is  hardly  commendable,  es- 
pecially in  the  case  of  dairy  cows. 

Composting  manure.  "Where  well  rotted  manure  is  desired, 
as  in  market  gardening,  the  practice  of  composting  is  in  general 
use.  This  is  largely  done  to  avoid  the  deleterious  heating  effect 
that  would  result  from  applying  large  quantities  of  raw  manure. 
In  addition  it  is  sometimes  resorted  to  in  order  to  destroy  noxious 
weed  seeds.  A  favorite  method  with  some  market  gardeners  is 
to  compost  the  manure  with  earth,  peat,  or  muck.  This  is  done 
by  making  a  foundation  of  about  6  inches  of  dirt,  and  on  top  of 
this  placing  alternate  layers  of  manure  and  soil,  moistening  the 
mass  as  the  heap  grows.  The  mass  is  finally  covered  with  a  thin 
layer  of  earth  to  prevent  loss  of  nitrogen.  After  about  2  months 
the  pile  should  be  turned  over,  the  materials  well  mixed  and  more 
water  added,  if  necessary,  to  keep  the  compost  moist.  Sometimes 
sod  is  used  in  place  of  the  soil,  which  gives  a  fibrous  compost  very 
desirable  for  pot  and  bench  work.  Refuse  materials,  such  as 
kitchen  waste,  dead  animals,  etc.,  can  be  added  with  advantage 
to  the  compost  heap,  thereby  enriching  the  mass  and  disposing  of 
such  materials  without  the  production  of  offensive  odors.  Where 
further  enrichment  is  necessary,  it  is  good  practice  to  add  bone 
meal  or  rock  phosphate  (floats)  and  one  of  the  potash  salts  to 
the  heap.  In  this  way  the  plant  food  in  the  phosphates  is  made 
more  available  to  plants  and  the  compost  more  valuable. 

When  it  is  desired  to  produce  well  rotted  manure  in  a  very 
short  time,  a  small  quantity  of  slaked  lime  can  be  mixed  with  the 
fresh  manure.  This  occasions  a  rapid  decay  of  the  mass,  but  as 
it  also  entails  a  loss  of  more  or  less  nitrogen,  the  method  is  not 
to  be  recommended  for  general  use. 


Agricultural  Chemistry 

Applying  manure.  A  manure  can  be  effective  only  when  its 
constituents  are  brought  into  contact  with  the  roots  of  the  crop. 
To  obtain  this  contact  to  its  fullest  extent,  the  manure  must  be 
thoroughly  and  evenly  distributed  throughout  the  depth  of  the 
soil  mainly  occupied  by  the  roots.  For  this  reason  it  appears 
best,  when  possible,  to  apply  the  fertilizers  to  the  surface  as  a 
top  dressing,  in  order  that  the  soluble  plant  food  as  it  descends 
may  come  in  contact  with  the  plant  roots.  The  manure  to  be 
used  this  way  must  be  fine  or  well  rotted,  but  even  fresh  manure 
can  be  so  utilized  where  cut  straw  or  other  fine  material  has  been 
used  for  bedding.  The  practice  of  applying  the  manure  directly 
after  plowing  and  thoroughly,  incorporating  it  with  the  soil  by 
the  use  of  the  harrow  or  cultivator  is  a  good  one. 

Spreading  the  manure  and  allowing  it  to  lie  on  the  surface 
should  be  practiced  only  on  level  fields  where  there  is  no  danger 
*T-om  surface  washing.  It  has  been  claimed  that  when  manure 


A  poor  way  of  using  good  manure. 

is  spread  broadcast  and  allowed  to  lie  on  the  surface,  there  may 
be  serious  loss  of  ammonia  into  the  air,  but  experiments  have 
shown  that  loss  from  this  cause  must  be  very  small.  Manure 
made  during  the  winter  and  hauled  directly  to  the  field  and 
spread  on  areas  that  are  fairly  level,  whether  fall  plowed  or  on 
sod  to  be  turned  under  in  the  spring,  is  most  economical  of  labor 
and  conserves  most  efficiently  the  valuable  fertilizing  materials. 
It  may  even  be  spread  on  the  snow,  where  it  is  not  too  deep,  with- 


Farm  Manure 


145 


out  serious  loss.     The  loss  is  certainly  less  than  when  thrown  in 
the  open  barn  yard. 

Manure  should  be  spread.  The  very  common  practice  of 
hauling  manure  to  the  field,  there  to  be  thrown  into  heaps,  has 
several  serious  objections.  In  the  first  place  it  increases  the 
work  entailed  in  spreading,  as  it  must  be  handled  twice.  When 
manure  is  so  piled  there  is  danger  of  injurious  fermentations, 
with  consequent  losses  of  nitrogen.  In  addition,  the  leaching 
from  such  piles  increases  the  amount  of  plant  food  directly  be- 
neath and  hence  produces  a  rank  growth.  It  is  not  uncommon 
to  find  the  next  season 's  crop  spotted  by  a  more  luxuriant  growth 
and  deeper  green  color  on  the  areas  where  the  manure  heaps  have 
been  placed.  This  condition  is  highly  undesirable,  as  it  causes 
the  crop  to  mature  at  different  ages  and  also  endangers  loss  by 
lodging.  A  crop  with  a  large  plant-food  supply  will  have  a 


Uneven  grain  and  grass.     This  bad  condition  comes  from  leaving  the 
manure  in  small  piles.     It  should  be  spread  when  hauled. 

longer  season  of  growth  than  one  with  a  meagre  supply.  If  the 
manure  is  spread  directly  from  the  wagon,  the  danger  of  uneven- 
ness  of  growth  is  largely  avoided  and  the  cost  of  labor  reduced. 
When  very  coarse  manure  is  used,  it  is  advantageous  to  supple- 


146  Agricultural  Chemistry 

ment  the  spreading  from  the  wagon  by  the  use  of  a  drag  that 
will. break  up  the  larger  lumps  and  thus  spread  it  more  uni- 
formly. 

Depth  to  cover  manure.  Where  the  manure  is  so  coarse  as  to 
interfere  with  tillage,  it  will  become  necessary  to  plow  it  under. 
Judgment  must  be  exercised  as  to  the  depth  to  which  it  should 
be  covered.  As  a  general  rule,  it  should  not  be  so  deep  as  to 
prevent  access  of  air  and  moisture,  which  are  necessary  to  insure 
fermentation  and  nitrification.  In  clay  soils  it  is  possible  to 
bury  the  manure  so  deeply  as  to  prevent  decay,  while  in  open 
sandy  soils  this  danger  is  not  so  great.  In  very  compact  soils  it 
has  been  recommended  that  the  depth  should  not  exceed  4  inches. 
During  very  dry  seasons  much  harm  may  result  from  plowing 
under  large  amounts  of  coarse  manure,  as  there  may  not  be  suf- 
ficient moisture  in  the  soil  to  bring  about  the  decay  of  the  organic 
matter.  This  undecayed  material  may  result  in  a  physical  in- 
jury to  the  soil. 

Applied  to  sod.  A  practice  that  is  highly  recommended  is  to 
apply  the  manure  as  it  is  made  to  meadow  or  sod  land  that  is 
to  be  plowed  and  planted  the  following  spring.  In  this  way 
what  is  applied  .in  summer  or  early  fall  is  partly  used  by  the 
growing  crop,  thus  avoiding  losses,  and  when  the  sod  is  plowed 
under  the  entire  plant  food  can  be  used  by  the  succeeding  crop. 
Manure  applied  to  pasture  or  meadows  during  the  summer  or  fall 
aids  in  conserving  the  moisture  by  its  action  as  a  mulch,  as  well 
as  supplying  plant  food  and  inducing  a  longer  season  of  growth. 

Fresh  and  rotted  manure.  The  form  in  which  manure  should 
be  applied  is  determined  largely  by  the  soil  on  which  it  is  to  be 
used.  On  heavy  soils  containing  large  amounts  of  clay,  more 
benefit  will  be  derived  from  fresh  manures  than  from  those  that 
are  well  rotted.  The  fresh  manure  warms  these  cold  soils,  makes 
them  more  porous,  and  the  fermentations  that  take  place  during 
decay  tend  to  make  the  soil  more  mellow. 

On  light  or  sandy  soils,  on  the  other  hand,  those  manures  that 
are  well  rotted  will  be  found  most  beneficial.  Such  soils  are 
likely  to  suffer  from  the  drying  and  heating  effect  of  raw,  coarse 


Farm  Manure  147 

manure,  and  to  have  their  porosity  increased  to  an  undesirable 
extent.  While  it  is  doubtful  if  moderate  quantities  of  fresh  ma- 
nure are  seriously  injurious  to  these  soils,  nevertheless,  if  applied 
in  large  quantities,  it  is  much  safer  to  have  the  manure  well 
rotted.  It  will  then  improve  the  mechanical  condition  of  the  soil 
and  increase  its  water  retaining  power. 

Fresh  manure  has  a  forcing  effect  and  tends  to  produce  stems 
and  leaves  at  the  expense  of  fruit  and  grain.  It  is  therefore 
better  for  early  garden  truck,  grasses  and  forage  plants  than  for 
cereals  or  fruits.  Corn  is  usually  benefited  by  liberal  applica- 
tions of  fresh  manure.  In  fact  it  may  be  said  that  when  in  doubt 
as  to  where  to  apply  the  manure,  use  it  on  corn.  It  is  claimed 
that  fresh  manure  is  injurious  to  sugar  beets  and  tobacco,  pro- 
ducing a  large  beet  of  low  sugar  content  and  a  coarse  and  un- 
desirable tobacco  leaf.  It  is  a  well  known  fact  that  raw  manure 
in  large  quantities  is  likely  to  cause  lodging  with  the  small  grains, 
such  as  barley,  oats  and  wheat.  In  the  case  of  sugar  beets,  ex- 
periments with  fresh  manure  at  the  New  York  State  Experiment 
Station  have  given  beets  of  high  sugar  content  and  without  rank 
leaf  growth,  results  at  variance  with  those  of  European  experi- 
ments. Climate  and  soil  are  probably  very  important  factors  in 
determining  what  will  be  the  comparative  results  with  the  two 
kinds  of  manure. 

Instead  of  using  the  manure  directly  on  the  small  grains,  it 
is  good  practice,  where  corn  is  grown,  to  apply  it  liberally  to  that 
crop  and  plant  the  field  to  the  smaller  grains  the  following  year. 
When  this  is  done  the  danger  from  rank  growth  is  minimized. 

Rate  of  application.  As  to  the  rate  at  which  manure  should 
be  applied,  no  fixed  rule  can  be  given.  It  will  depend  upon  the 
character  of  the  soil,  the  quality  of  the  manure,  the  nature  of 
the  crop  and  the  frequency  of  application.  German  authorities 
consider  7  to  10  tons  light,  and  20  tons  or  more  heavy,  applica- 
tions. Sir  Henry  Gilbert  considered  14  tons  per  acre,  annually, 
excessive  for  wheat  and  barley.  For  ordinary  farm  crops  it  is 
not  customary  to  use  more  than  8  to  10  tons  per  acre.  As,  a 
general  principle  it  may  be  stated  that  frequent  light  dressings 


148 


Agricultural  Chemistry 


pay  better  than  very  large  ones  at  long  intervals.  Too  liberal 
applications  are  wasteful.  The  amount  of  manure  produced  on 
the  average  farm  is  so  small  compared  with  the  land  to  be  fer- 
tilized that  it  would  be  utterly  impossible  to  spread  it  over  all 
the  farm  yearly.  For  this  reason  it  is  considered  good  practice 
to  apply  the  manure  to  one  crop  in  a  rotation,  thus  covering  only 
part  of  the  farm  each  year.  The  following  three-year  plan  of 
rotation  will  explain  the  above  statement ;  corn,  1  year ;  grain,  1 
year;  clover,  1  year;  the  manure  is  applied  to  the  clover  sod. 
The  following  table  brings  out  clearly  the  relation  of  plant  food 
removed  by  such  a  rotation  as  described  above,  and  the  quantity 
returned  by  the  application  of  10  or  15  tons  of  farm  manure  of 
average  composition  once  in  3  years.  No  account  is  taken  of 
losses  by  drainage  or  the  gain  in  nitrogen  to  the  soil  of  probably 
50  pounds  per  acre,  by  the  growth  of  the  clover. 


Wt.  crop 
dry 
per  acre 

Nitrogen 

Phos- 
phoric 
Acid 

Potash 

Corn  grain  30  bushels  

Lbs. 
1500 

Lbs. 
28.0 

Lbs. 
10.0 

Lbs. 
6.5 

Corn  stalks  

1877 

15.0 

8.0 

29.8 

Barley  grain  40  bushels  • 

1747 

35.0 

16.0 

9.8 

Barlev  straw  

2080 

14.0 

4.7 

25.9 

Red  clover  2  tons  

3763 

98-0 

24.9 

83.4 

Total  removed  

190.0 

63.6 

155.4 

Manure  10  tons    

100.0 

50.0 

100.0 

Manure  15  tons    

150.0 

75.0 

150.0 

We  see  from  this  table  that  it  would  require  once  in  3  years 
the  application  of  about  15  tons  of  manure  of  average  composi- 
tion to  replace  the  plant  food  removed  by  th'e  three  crops. 

Relation  of  manure  to  maintenance  of  fertility.  At  the  Rot- 
hamsted  Experiment  Station,  England,  experiments  to  determine 
the  relative  value  of  farm  yard  manure  and  commercial  fertili- 


Farm  Manure 


149 


zers  have  been  carried  on  over  a  very  long  period  of  time.  On 
certain  plots,  crops  have  been  grown  continuously  with  no  fer- 
tilizer, on  other  plots  with  barn  yard  manure  at  the  rate  of  14 
tons  per  acre  annually,  and  on  still  others,  various  combinations 
of  commercial  fertilizers  have  been  tested.  The  tests  extend 
over  40  years  and  are  given  in  the  following  table  as  averages  of 
five  8-year  periods. 

Comparative  Effect  of  Manure  and  Commercial  Fertilizers 


Barley  —  Bushels  per  acre 

Wheat  —  Bushels  per  acre 

No 
Manure 

Manure 

Com- 
mercial 
Fer- 
tilizers 

No 
Manure 

Manure 

Com- 
mercial 
Fer- 
tilizers 

1st  8  years  

24 
18 
14 
14 
11 

16 

44 
52 
49 
52 
44 

48 

48 
51 
45 
42 
41 

45 

16 
13 

12 
10 

12 

13 

34 
35 
35 

28 
39 

34 

36 
39 
36 
32 

38 

36 

2nd  8  years  

3rd  8  years  

4th  8  years  

5th  8  years  

Average  (40  years) 

It  will  be  seen  that  there  was  practically  no  difference  between 
the  plots  dressed  with  farm  manure  and  those  receiving  commer- 
cial fertilizers.  In  fact  the  test  was  hardly  fair  to  the  manure, 
as  excessive  quantities  of  commercial  fertilizers  were  applied. 
The  amount  of  nitrogen  added  to  the  wheat  was  equal  to  that 
contained  in  800  pounds  of  nitrate  of  soda,  an  excessive  amount. 
It  is  believed  by  some  authorities  that  had  the  experiment  been 
conducted  in  America  the  result  would  have  been  more  favorable 
to  the  barn  yard  manure.  This  judgment  is  based  on  the  belief 
that  nitrification,  due  to  the  influence  of  climate,  would  be  more 
rapid  in  this  country  than  in  England. 

Lasting  effect  of  manure.  Barn  yard  manure,  because  of  its 
slow-decomposing  organic  matter,  has  a  lasting  effect  when  ap- 


150 


Agricultural  Chemistry 


plied  to  the  soil.  Where,  at  Rothamsted,  a  plot  was  manured  an- 
nually for  20  years,  and  then  received  no  manure  for  the  next 
20  years,  this  effect  is  clearly  shown.  The  following  table  illus- 
trates this  effect.  The  figures  represent  the  action  of  the  residual 
manure,  as  no  fertilizer  was  added  during  the  period  covered  by 
the  table.  The  crop  grown  was  barley  and  is  expressed  in  bushels 
per  acre. 

Lasting  Effect  of  Manure 


Unmannred 

Effect  residual 
manure 

First      five  year?  

13 

39 

Second  five  years    

14 

29 

Third    five  year;~  

14 

30 

Fourth  five  years  

12 

23 

Average  (20  years)  

13.2 

30 

The  table  shows  that  the  effect  of  the  manure  was  perceptible 
in  yield  for  at  least  20  years  after  the  last  application.  In  fact 
the  value  of  barn  yard  manure  cannot  be  estimated  on  the  basis 
of  the  plant  food  it  contains  alone.  It  has  a  greater  value  than 
that  because  of  its  improvement  on  the  physical  conditions  of 
the  soil  and  the  increased  fermentations  which  result  from  its 
application.  It  is  always  a  safe  fertilizer  for  the  inexperienced 
farmer,  as  there  is  little  danger  of  lasting  injury  from  its  use, 
while  it  is  possible  to  use  commercial  fertilizers  in  such  a  way 
as  to  make  the  soil  poorer  after  their  use  than  it  was  before. 

Effect  of  style  of  farming  on  fertility.  Prominent  author- 
ities in  agriculture  believe  that  in  a  system  of  strictly  animal  hus- 
bandry, where  nothing  is  sold  from  the  farm  except  animals  or 
animal  products,  and  all  the  manure  properly  saved  and  utilized, 
the  fertility  of  the  land  may  be  maintained  indefinitely  without 
the  purchase  of  commercial  fertilizers.  It  should  be  remembered 
that  a  positive  balance  of  plant  food- could  not  be  maintained  in 


Farm  Manure 


151 


this  way  unless  additional  feeding  materials  were  purchased  and 
fed  on  the  farm.  This  is  due  to  the  20  per  cent  loss  of  fertilizing 
materials  contained  in  the  growing  animals  and  milk  produced. 
While  there  may  be  large  stores  of  potential  plant  food  in  the 
soil  which  could  make  up  the  20  per  cent  yearly  deficit  and  main- 
tain average  crop  production,  nevertheless,  a  permanent  agri- 
culture could  not  be  founded  on  such  practice. 

In  systems  of  animal  husbandry  it  is  the  rule  to  purchase  ad- 
ditional feeding  stuffs.  The  amount  of  wheat  bran  necessary  to 
offset  the  losses  on  a  farm  from  which  live  stock  and  milk  are 
sold,  is  shown  in  the  following  table.  The  calculations  are  based 
on  what  a  farm  of  160  to  200  acres  could  do.  Only  potash  and 
phosphoric  acid  are  considered,  as  the  supply  of  nitrogen  for 
plant  production  can  be  maintained  through  the  growth  of  legu- 
minous crops. 

Compensation  of  Losses  on  a  Farm  "by  Purchase  of  Wheat  Bran 


Potash 

Phosphoric  Acid 

Live  stock  sold  

Lbs. 
20,  000 

Lbs. 
40 

Lbs. 
300 

Milk  sold  

146,  000 

250 

262 

Total  

290 

562 

Bran  Purchased  

18,000 

306 

630 

The  table  brings  out  the  fact  that  9  tons  of  wheat  bran  would 
offset  the  losses  sustained  by  the  sale  of  farm  animals  and  milk. 
Where  cream  is  sold  instead  of  milk,  the  amount  of  wheat  bran 
necessary  to  supply  the  loss  of  potash  and  phosphoric  acid  in  the 
stock  sold  would  be  about  5  tons. 

It  must  be  clear  to  the  student  from  what  has  already  been 
said,  that  losses  in  fertility  are  greater  in  any  system  of  farming, 
where  the  crops  are  sold  from  the  farm  than  when  some  form  of 
animal  husbandry  is  followed,  especially  if  no  commercial  fer- 


152 


Agricultural  Chemistry 


tilizers  are  purchased.  To  illustrate  this  point  more  fully,  the 
following  table  adapted  from  a  Minnesota  bulletin  is  given. 
Four  farms,  each  containing  160  acres,  were  assumed.  On  the 
first  nothing  but  grain  was  raised  and  sold.  The  second  was 
about  equally  divided  between  grain  and  stock  farming,  and  the 
third  and  fourth  were  devoted  exclusively  to  stock  raising  and 
dairying,  respectively.  In  the  last  two  cases  a  small  amount  of 
the  farm  produce  was  exchanged  for  mill  products,  which  ac- 
counts for  the  slight  gain  in  phosphoric  acid,  but  it  was  assumed 
that  no  other  concentrates  or  fertilizers  were  purchased.  The 
decidedly  smaller  loss  of  nitrogen  on  the  second  farm  and  the 
actual  increase  of  nitrogen  on  the  stock  and  dairy  farms  are  due 
to  fixation  of  nitrogen  from  the  growth  of  clover.  The  figures 
represent  pounds  of  fertilizing  material  lost  or  gained  on  the 
farm  in  1  year. 

Effect  of  Style  of  Farming  on  Fertility 


Kind  of  farming 

Gain  or  loss  in  fertility 

Nitrogen 

Phosphoric  Acid 

Potash 

All  grain  

Lbs. 
-5000 
-1100 
+1100 
+1200 

Lbs. 

-2500 
-1000 
+    50 
+    75 

Lbs. 
-4200 
-1000 
-    60 
-     85 

Mixed  •  . 

Stock  

Dairy  

Green  manuring.  The  lowered  crop  producing  power  of  a 
soil  is  in  many  instances  due  to  the  rapid  decrease  in  the  amount 
of  humus  which  it  contains.  Humus  is  formed  in  most  cases 
from  the  plants  which  have  previously  grown  on  the  field  and 
have  later  become  a  part  of  the  soil.  It  may  be  produced  from 
.animal  or  vegetable  material  added  as  manure.  Virgin  soils  are 
rich  in  humus,  but  continued  cropping  with  no  provision  for 
maintaining  the  supply  may  result  in  its  being  decreased  from 


Farm  Manure 


153 


one-third  to  one-half  in  a  period  of  not  more  than  15  years. 
Humus  is  of  importance  because  it  is  a  storehouse  of  plant  food, 
especially  nitrogen.  Most  of  the  nitrogen  of  the  soil  is  contained 
in  the  more  or  less  decomposed  organic  matter  present. 

Plowing  under  green  crops,  grown  for  that  purpose,  is  one  of 
the  oldest  means  of  increasing  the  humus  content  of  soil.  By 
this  practice,  not  only  is  the  soil  enriched  with  carbonaceous  mat- 
ter derived  from  the  air,  but  a  considerable  amount  of  nitrates 
which  would  have  been  formed  by  nitrification  during  the  growth 
of  the  crop,  is  assimilated,  converted  into  complex  organic  com- 
pounds in  the  plant  and  restored  to  the  soil.  Without  the  crop 
these  nitrates  would  have  been  to  a  large  extent  lost  by  drainage. 
The  planting  of  catch  crops  for  this  purpose  is  best  done  in  the 
autumn,  since  nitrification  is  then  very  rapid  and  loss  from  wash- 
ing out  of  nitrates  by  winter  rains  is  to  a  great  extent  prevented. 

For  gT-een  manuring,  two  classes  of  crops  are  in  common  use. 


Experiments  showing  that  "green  manuring"  with  legume  plants  can 
supply  all  the  nitrogen  needed  by  a  succeeding  crop  (after  Wagner). 


154  Agricultural  Chemistry 

To  the  first  class  belong  such  crops  as  buckwheat,  mustard,  rye, 
rape,  etc.  These  kinds  of  plants  are  efficient  in  restoring  car- 
bonaceous matter  and  what  nitrogen  was  available  for  their 
growth.  They  have  added  no  essential  element  of  plant  growth. 
They  should  be  plowed  under  before  seed  is  produced  or  other- 
wise the  land  would  be  fouled  for  the  next  year. 

To  the  second  class  belong  the  legumes.  They  have  all  the  ad- 
vantages of  the  first  class,  but  in  addition,  increase  the  amount 
of  nitrogen  in  the  soil.  Those  most  often  recommended  are  red 
clover,  the  lupines,  cow  peas,  crimson  clover,  soy  bean  and  the 
ordinary  field  bean  and  field  pea.  Red  clover  is  the  one  most 
commonly  used.  They  produce  good  results  even  when  the  crop 
is  harvested  and  the  stubble  plowed  under.  At  the  Rothamsted 
Experiment  Station  it  has  been  estimated  that  50  pounds  or  more 
of  nitrogen  per  acre  is  added  to  the  soil  annually  in  the  roots  and 
stubble  of  clover  alone. 

Under  certain  conditions  green  manuring  may  be  attended  by 
dangers.  In  a  dry  season  the  growth  of  a  crop  to  plow  under 
may  decrease  the  moisture  content  of  the  soil  to  a  point  that  is 
harmful  to  the  succeeding  crop.  In  such  a  season  there  may  also 
be  insufficient  moisture  in  the  soil  to  bring  about  the  decomposi- 
tion of  the  organic  matter  which  is  turned  under.  "When  green 
manuring  is  practiced  in  a  dry  season,  the  land  should  be  rolled 
so  as  to  establish  capillarity  as  far  as  possible. 

Where  systems  of  stock  farming  are  practiced,  it  appears  to 
be  a  wasteful  method  to  plow  under  green  crops  which  may  be 
suitable  for  feed.  It  would  be  found  more  profitable  to  feed 
them  to  the  animal,  carefully  save  the  manure  and  return  it  to 
the  fields.  Green  manuring  will  prove  desirable  in  any  system 
of  farming  where  the  crops  are  sold  from  the  farm.  On  the 
other  hand,  when  the  farmer  is  engaged  in  stock  farming  and 
the  crops  are  of  value  as  feeds,  then  turning  them  under  must 
be  considered  a  wasteful  practice. 


CHAPTER  Vli 

COMMERCIAL  FERTILIZERS 

It  is  neither  possible  nor  necessary  for  all  farmers  to  engage 
in  stock  raising  or  dairying  in  order  to  maintain  the  fertility  of 
the  land.  While  it  is  possible,  as  has  been  described,  to  main- 
tain without  the  purchase  of  commercial  fertilizers,  a  positive 
balance  of  plant  food  on  the  farm  in  the  practice  of  the  above 
systems,  it  is  manifestly  impossible  to  do  so  in  a  system  of  grain 
farming  where  the  crops  raised  are  all  sold  from  the  farm.  In 
the  latter  system  recourse  to  commercial  fertilizers,  supplemented 
by  green  manuring  for  the  purpose  of  maintaining  the  humus 
content  of  the  soil,  must  be  made  sooner  or  later. 

At  the  present  time  probably  $120,000,000  are  spent  annually 
in  the  purchase  of  fertilizers  in  the  United  States,  and  it  is  no 
exaggeration  to  say  that  fully  one-half  of  this  is  money  thrown 
away.  This  is  not  an  argument  against  their  use,  but  simply 
means  that  they  should  be  purchased  with  judgment  and  not  used 
at  all  until  actual  investigation  has  shown  them  to  be  necessary. 
Plant  food  not  the  only  factor  in  crop  growth.  It  should  be 
remembered  that  other  factors  than  plant-food  supply  enter  into 
the  production  of  large  crops.  Improper  physical  condition  of 
the  soil,  lack  of  moisture,  deficiency  of  hum,us,  unsuitable  soil  re- 
action, toxic  substances,  unfavorable  weather,  etc.,  all  may  inter- 
fere with  the  normal  and  vigorous  development  of  the  plant  and 
thus  cause  diminished  crop  returns,  even  when  the  plant  has 
within  reach  all  the  food  it  needs.  These  unfavorable  conditions 
may  partly  be  ameliorated  through  means  available  to  man,  such 
as  draining,  irrigating,  harrowing,  liming,  etc.  Too  frequently 
fertilizers  are  made  to  take  the  place  of  tillage  when  they  should 
be  used  to  supplement  it.  That  is,  fertilizers  are  more  likely  to 


156  Agricultural  Chemistry 

give  profitable  results  when  used  in  conjunction  with  an  excel- 
lent physical  condition  of  the  soil,  and  the  man  who  would  ob- 
tain best  results  without  fertilizers  is  the  one  most  likely  to 
realize  a  profit  from  their  use.  "The  fact  that  fertilizers  can 
now  be  easily  secured,  and  the  ease  of  application,  have  encour- 
aged a  careless  use,  rather  than  a  thoughtful  expenditure  of  an 
equivalent  amount  of  money  or  energy  in  the  proper  prepara- 
tion of  the  soil.  Of  course  it  does  not  follow  that  no  returns  are 
secured  from  plant  food  applied  under  unfavorable  conditions, 
though  full  returns  cannot  be  secured  under  such  circumstances. 
Good  plant  food  is  wasted  and  the  profit  possible  to  be  derived  is 
largely  reduced. ' '  Again,  in  many  instances,  the  ease  with  which 
commercial  fertilizers  can  be  secured  tends  to  a  neglect  of  the 
home  resources  and  one  far  too  commonly  sees  the  waste  of  farm 
manure  and  the  purchase  of  commercial  fertilizers  practiced  on 
the  same  farm. 

What  commercial  fertilizers  contain.  Investigation  and  ex- 
perience have  shown  that  in  most  instances  increased  production 
has  resulted  from  the  addition  to  the  soil  of  but  three  of  the  es- 
sential substances  found  in  plants;  namely:  nitrogen,  phosphoric 
acid  and  potash.  It  has  been  shown  that  in  normal  soils  there 
are  probably  sufficient  quantities  of  all  the  other  elements  which 
the  plant  requires.  It  was  customary,  soon  after  the  time  of  Lie- 
big,  for  agricultural  investigators  to  add  all  the  elements  essen- 
tial to  plant  growth,  but  practice  soon  showed  that  to  be  unnec- 
essary, for  the  reason  stated  above.  Consequently  commercial 
fertilizers,  as  placed  on  the  market  today,  contain  only  nitrogen, 
phosphoric  acid  or  potash,  or  mixtures  of  these  ingredients  and 
these  are  the  only  elements  giving  the  fertilizer  commercial  value. 

Commercial  fertilizers  are  made  from  a  few  basal  materials 
which  are  articles  of  commerce.  Some  of  these  materials  contain 
only  one  of  the  essential  ingredients  of  a  fertilizer,  while  others 
contain  two,  but  usually  one  is  in  such  excess  that  the  material 
is  used  chiefly  to  furnish  but  the  one  element. 

The  complete  fertilizer  consists  of  two  or  more  of  these  basal 


Commercial  Fertilizers 


157 


materials  mixed  together  to  give  the  desired  per  cent  of  nitrogen, 
phosphoric  acid  and  potash. 

Nitrogenous  fertilizers.     This  group  of  substances  may  be 
divided  into  two  classes:  (1)  Inorganic  or  mineral  substances; 


Complete 
Fertilizer 


Without 
Phosphoric  Acid 


Without 
Potash 


Without 
Nitrogen 


Effect  of  fertilizer  constituents  upon  oats  grown  on  clay  soil.  Note  the 
scarcity  of  foliage  where  no  nitrogen  was  supplied  and  the  low  yield 
of  grain  where  phosphoric  acid  was  lacking. 

(2)  organic  substances  derived  from  animal  or  vegetable  ma- 
terials. The  inorganic  materials  most  commonly  used  are  sul- 
phate of  ammonia,  nitrate  of  soda  and  nitrate  of  potash. 

Sulphate  of  ammonia,  (NH4)2S04.     This  material  is  from  the 


158  Agricultural  Chemistry 

gas  works  and  is  obtained  as  a  by-product  in  the  manufacture  of 
illuminating  gas.  It  is  the  most  concentrated  nitrogenous  ma- 
terial in  the  market  and  contains  from  20  to  23  per  cent  of  ni- 
trogen, equivalent  to  about  25  per  cent  of  ammonia.  It  is  very 
soluble  in  water }  does  not  readily  leach  out  of  the  soil,  and  un- 
dergoes nitrification  very  quickly,  being  converted  into  nitrates. 
However,  some  plants  may  take  a  part  of  their  nitrogen  supply 
directly  as  ammonium  salts,  when  so  applied.  The  sulphate 
gives  good  results  on  soils  containing  plenty  of  lime.  It  should 
not  be  used  on  soils  deficient  in  lime,  because  of  its  tendency  to 
leave  the  soil  acid. 

Nitrate  of  soda,  NaN03.  This  fertilizer  is  known  under  the 
name  of  "Chili  salt  petre"  and  occurs  in  deposits  of  consider- 
able extent  in  Chili.  "When  crude  it  is  called  "caliche"  and 
contains  varying  amounts  of  impurities,  chiefly  common  salt.  It 
is  freed  from  these  impurities  by  solution  and  crystallization  and 
when  put  upon  the  market  contains  from  95  to  97  per  cent  of 
nitrate  of  soda.  This  final  product  contains  from  15  to  16  per 
cent  of  nitrogen.  Chili  supplies  over  a  million  tons  of  nitrate  a 
year  to  be  used  as  a  fertilizer.  This  substance  contains  its  ni- 
trogen in  the  most  readily  assimilable  form,  and  in  the  form  into 
which  most  other  nitrogenous  bodies  must  be  converted  before 
they  are  taken  up  by  the  plant.  It  is  not  fixed  completely  by 
the  soil  and  unless  growing  crops  are  at  hand  to  take  it  up,  it 
will  be  leached  out  by  rains.  Consequently  it  should  be  applied 
as  a  top  dressing  and  in  not  too  heavy  applications.  It  is  bsst 
applied  early  in  the  spring  soon  after  the  plants  have  started 
their  growth  and  should  be  mixed  with  at  least  double  its  weight 
of  soil  before  being  applied,  as  otherwise  harm  to  the  plants  may 
result.  It  should  not  be  applied  to  grain  crops  late  in  the  season. 

Nitrate  of  potash,  KN03.  This  is  commonly  known  as  salt 
petre  and  is  one  of  the  most  concentrated  fertilizing  materials 
we  have,  since  it  contains  both  nitrogen  and  potash  in  available 
forms.  It  contains  about  13  per  cent  of  nitrogen  and  from  42 
to  45  per  cent  of  potash.  It  is  generally  too  expensive  to  use  for 


Commercial  Fertilizers  159 

manurial  purposes,  as  it  is  used  very  extensively  in  various  man- 
ufacturing processes. 

Calcium  nitrate,  Ca(N03)24H20.  This  product  is  manufac- 
tured by  passing  strong  electric  discharges  through  air.  By  this 
means  oxides  of  nitrogen  are  produced  by  the  union  of  oxygen 
and  nitrogen  thus: — 

2NO+02=2N02 
H,0+3N02=NO+2HN03 

These  gases  are  absorbed  in  water  with  the  production  of  nitric 
acid.  This  acid  is  then  led  into  milk  of  lime,  which  results  in 
the  formation  of  calcium  nitrate.  The  product  is  next  concen- 
trated until  it  solidifies  as  a  material  containing  about  13  per 
cent  of  nitrogen.  At  the  present  time  it  is  almost  entirely  pro- 
duced in  Norway,  where  cheap  water  power  is  available,  and  in 
cheapness  compares  favorably  with  nitrate  of  soda.  As  a  fer- 
tilizer and  as  a  source  of  nitrogen  it  JIMS  given  excellent  results. 
Calcium  cyanamide,  CaCN2,  is  a  comparatively  new  nitrogen- 
containing  fertilizer  and  is  produced  by  heating  calcium  carbide 
in  a  current  of  air  from  which  the  oxygen  has  been  removed 
thus : — 

CaC2+N2=CaCN2+C 

When  used  as  a  manure  it  has  in  many  cases  given  as  good  re- 
sults as  the  same  amount  of  nitrogen  applied  as  nitrate  of  soda 
or  ammonium  sulphate.  Because  of  its  injurious  effect  on  ger- 
minating seeds,  it  should  be  incorporated  with  the  soil  a  week  or 
so  before  any  seed  is  sown.  It  contains  about  20  per  cent  of 
nitrogen,  and  is  to-day  produced  in  limited  quantities  in  this 
country.  It  decomposes  in  the  soil  as  follows: — 

CaCN2+3H20=2NH3+CaC03 

Organic  nitrogenous  materials.  In  order  to  bring  out  clearly 
the  relative  value  of  this  class  of  fertilizing  materials  they  will 
be  discussed  under  the  following  heads;  first,  those  materials  in 
which  the  nitrogen  becomes  readily  available  in  a  comparatively 


160  Agricultural  Chemistry 

short  time  by  decomposition  in  the  soil;  second,  those  materials 
which  undergo  fermentation  very  slowly  and  the  nitrogen  of 
which  only  becomes  available  after  a  long  time.  Readily  avail- 
able materials  include  such  products  a,s  dried  blood,  meat  scraps, 
tankage,  dried  fish  or  fish  scrap,  cotton-seed  meal  and  castor 
pomace. 

Dried  blood.  This  material  is  obtained  by  drying  the  blood 
from  slaughter  houses.  Two  grades  are  found  on  the  market, 
known  as  red  and  black  blood.  The  red  variety  has  been  more 
carefully  dried,  while  the  black  blood  has  resulted  from  a  too 
rapid  drying.  The  red  blood  contains  from  13  to  14  per  cent  of 
nitrogen,  while  the  black  variety  is  less  constant  in  composition 
and  contains  from  6  to  12  per  cent.  Dried  blood  ferments  very 
readily  in  the  soil  and  is  one  of  the  most  valuable  organic  ma- 
terials. 

Meat  scrap  or  meat  meal.  This  is  a  packing  house  product 
and  consists  of  various  parts  of  animal  bodies  that  have  been 
kept  separate  from  the  tankage.  It  is  rather  variable  in  com- 
position, containing  usually  from  10  to  12  per  cent  of  nitrogen, 
with  a  small  amount  of  phosphoric  acid — about  3  per  cent.  It 
is  often  used  for  feeding  purposes,  as  well  as  for  fertilizer. 

Tankage.  This  is  a  general  mixture  of  the  refuse  material 
from  the  slaughter  houses.  It  has  usually  been  steam-cooked  in 
order  to  separate  the  fat  and  gelatine,  a  process  which  renders  it 
more  easily  fermentable  in  the  soil.  From  the  great  variations 
in  the  nature  of  the  materials  entering  into  its  make-up,  it  must 
of  necessity  have  a  variable  composition.  It  contains  from  4 
to  9  per  cent  of  nitrogen  and  from  3  to  12  per  cent  of  phosphoric 
acid.  It  is  a  valuable  form  of  fertilizer  as  it  supplies  the  crop 
with  both  nitrogen  and  phosphoric  acid. 

Dried  fish  and  fish  scrap.  Most  of  the  fish  fertilizers  are 
made  from  menhaden,  a  fish  that  is  caught  in  large  numbers 
along  the  Atlantic  coast.  The  fish  are  steamed  and  pressed  to 
extract  the  oil  and  the  remaining  "pomace"  is  dried  and  ground. 
This  material  contains  from  8  to  11  per  cent  of  nitrogen  and  3  to 
5  per  cent  of  phosphoric  acid.  Some  of  the  fish  fertilizers  con- 


Commercial  Fertilizers  161 

sist  of  the  residue  of  the  canning  factories,  but  these  are  not 
considered  so  valuable  as  those  derived  from  menhaden.  This 
material  readily  undergoes  nitrification  and  is  a  quick  acting 
fertilizer. 

Cotton-seed  meal.  This  is  obtained  by  removing  the  hulls 
and  oil  from  the  cotton  seed.  The  material  is  then  ground  and 
put  upon  the  market.  It  contains  about  7  per  cent  of  nitrogen, 
1.5  per  cent  of  phosphoric  acid,  and  2  per  cent  of  potash.  It  is 
too  good  a  food  material  to  be  used  as  a  fertilizer,  as  it  is  con- 
sidered one  of  the  best  concentrated  feeds  on  the  market.  Its 
value  as  a  feed  is  becoming  more  and  more  recognized  and  it  is 
only  a  question  of  time  when,  like  linseed  meal,  it  will  no  longer 
be  available  as  a  fertilizer. 

Castor  pomace  is  a  by-product  in  the  manufacture  of  castor 
oil.  It  contains  5.5  per  cent  of  nitrogen,  about  2  per  cent  of 
phosphoric  acid  and  1  per  cent  of  potash. 

Slowly  available  materials.  Under  this  head  are  classed  such 
materials  as  leather  meal,  hoof  and  horn  meal,  and  hair  and  wool 
waste. 

Leather.  This  is  a  waste  product  from  various  factories  and 
is  sold  as  raw  leather,  steamed  leather  and  roasted  leather;  it 
contains  about  7  per  cent  of  nitrogen  and  in  the  soil  decays  very 
slowly.  "When  finely  ground  it  is  sometimes  used  to  adulterate 
fertilizing  material. 

Hoof  and  horn  meal  is  a  by-product  resulting  from  the  mak- 
ing of  various  articles  from  hoofs  and  horns;  it  is  very  rich  in 
nitrogen,  carrying  about  14  per  cent,  but  decomposes  very  slowly 
in  the  soil. 

Hair.  This  is  another  product  from  slaughter  houses,  and 
when  dry  contains  from  9  to  14  per  cent  of  nitrogen.  It  is  very 
unavailable  and  should  not  be  used  in  its  natural  condition  for 
fertilizing  purposes. 

Wool  waste  is  the  waste  product  from  the  woolen  mills  and 
contains  from  5  to  6  per  cent  of  nitrogen  and  about  1  per  cent 
of 'potash.  It  is  essentially  the  wool  fibres  which  have  become 


162  Agricultural  CJiemistry 

so  short  by  repeated  spinning,  weaving,  etc.,  that  they  will  no 
longer  hold  together.     It  is  a  low  grade  fertilizer. 

In  many  states  all  the  above  resistant  materials  are  prohibited 
from  sale  as  fertilizers.  This  appears  just,  since  in  their  original 
form  they  decay  so  very  slowly  as  to  make  them  of  little  value 
as  food  for  plants.  In  more  modern  practice  these  materials  are 
digested  with  sulphuric  acid,  which  renders  the  nitrogen  soluble 
and  available. 

Experiments  indicate  that  if  nitrate  of  soda  is  rated  at  100 
per  cent,  the  availability  of  the  other  materials  will  be  as  fol- 
lows: 

Per  cent. 

Nitrate  of  soda 100 

Blood  and  cotton-seed  meal   70 

Fish  65 

Bone  and  tankage 60 

Leather,  hair,  wool  waste,  etc 2 — 30 

This  suggests  that  for  those  crops  which  begin  their  growth 
early  in  the  spring,  the  best  results  will  follow  the  use  of  Chili 
salt-petre,  as  the  soil  is  likely  to  be  poor  in  nitrates  and  the 
process  of  nitrification  slow  at  that  time.  Other  crops,  as  corn, 
for  example,  which  make  their  growth  after  the  season  is  well 
advanced,  can  use  the  slower  acting  fertilizers ;  as  can  those  crops 
which  occupy  the  ground  permanently. 

In  ordinary  farming  it  is  seldom  profitable  to  purchase  nitro- 
genous fertilizers,  for  the  nitrogen  of  the  soil  can  be  maintained 
by  means  of  farm  manures  and  the  proper  use  of  leguminous 
crops  in  the  rotation.  In  intensive  farming,  as  market  garden- 
ing, it  will  be  found  necessary  to  make  liberal  use  of  nitrogenous 
fertilizers. 

Phosphatic  fertilizers.  Materials  from  which  phosphoric  acid 
is  derived  are  called  phosphates.  Commercial  sources  of  the 
phosphoric  acid  of  fertilizers  are:  (1)  phosphate  rock;  (2)  bones 
and  bone  preparations;  (3)  basic  slag;  (4)  guano. 

Phosphoric  acid  is  found  in  these  materials  in  combination 
with  lime,  iron  and  alumina.  In  combination  with  lime  it  forms 
three  different  compounds;  (1)  insoluble  phosphate  of  lime; 


Commercial  Fertilizers  163 

(2)  soluble  phosphate  of  lime;  (3)  reverted  phosphate  of 
lime. 

Insoluble  phosphate  of  lime,  Ca3(P04)2,  is  known  as  "tri- 
calcium  phosphate,"  or  "bone  phosphate  of  lime"  and  is  com- 
posed of  three  parts  of  lime  in  combination  with  one  part  of 
phosphoric  acid.  It  is  insoluble  in  water  and  not  readily  avail- 
able to  plants.  The  principal  materials  found  on  the  market 
containing  this  form  of  phosphate  are: — South  Carolina  rock, 
Florida  rock,  Tennessee  rock,  bones  and  tankage.  They  contain 
from  25  to  30  per  cent  of  phosphoric  acid.  Ground  into  a  fine 
powder,  the  first  three  are  sometimes  sold  under  the  name  of 
"floats,"  which  on  account  of  its  fineness  of  division  has  given 
beneficial  results,  especially  when  mixed  with  stable  manure  or 
applied  to  soils  rich  in  organic  matter. 

Soluble  phosphate  of  lime,  CaH4(P04)2.  This  substance  is 
known  under  several  names,  as  "one-lime  phosphate,"  "acid- 
phosphate,"  "super-phosphate,"  "acidulated  rock,"  etc.  It 
is  the  result  of  treating  rock  phosphates  or  bones  with  sulphuric 
acid  thus: — 

Ca3(P04)2-f2H2S04=CaH4(P04)2+2CaS04 
By  this  process  the  sulphuric  acid  combines  with  2  parts  of  the 
lime,  forming  sulphate  of  lime  or  gypsum.  This  leaves  a  com- 
pound which  contains  1  part  of  lime  and  2  parts  of  water,  in 
combination  with  the  1  part  of  phosphoric  acid  which  was  con- 
tained in  the  tri-calcium  phosphate.  This  substance  is  soluble 
in  water,  readily  diffuses  in  the  soil,  and  is  in  the  most  available 
form  for  direct  use  by  the  plant.  A  good  sample  of  acid-phos- 
phate contains  about  16  per  cent  of  phosphoric  acid.  "While 
easily  dissolved  by  water,  it  is  not  leached  out,  as  several  con- 
stituents of  the  soil  such  as  humus,  lime,  iron  and  aluminum 
compounds  have  the  power  of  fixing  and  retaining  it  for  the  use 
of  plants. 

Reverted  phosphate  of  lime,  Ca,H2(P04)2.  In  making  su- 
per-phosphate the  whole  of  the  insoluble  phosphate  is  not  acted 
upon.  The  tri-calcium  phosphate  which  remains  after  the  treat- 
ment with  acid,  when  left  in  contact  with  a  comparatively  large 


164 


Agricultural  Chemistry 


amount  of  soluble  phosphate,  causes  a  reversion  of  some  of  the 
soluble  material  to  what  is  called  " reverted"  or  "gone  back" 
phosphate  as  for  example: — 

CaH4  (POJ  2+Ca3  (PO4)  2=2Ca2H2  (POJ  2 

It  is  also  known  as  "di-calcium"  phosphate,  "citrate-soluble," 
and  "precipitated  phosphate."  In  composition,  this  material 
falls  between  the  tri-calcium  and  mono-calcium  phophates.  It 
is  quite  insoluble  in  pure  water,  but  can  be  dissolved  by  weak 
acids,  and  by  water  containing  carbon  dioxide,  or  ammonium 
salts.  As  the  soil  moisture  contains  salts  in  solution,  as  well  as 
carbon  dioxide,  this  phosphate  is  readily  assimilated  by  plants 
and  is  considered  an  available  form.  This  form  of  phosphate  is 
considered  to  be  more  available  to  the  plant  than  the  insoluble 
or  natural  phosphate ;  hence,  the  soluble  and  reverted  phosphoric 
acids  taken  together  are  known  as  the  available  phosphoric  acid. 


Florida  rock-phosphate  mining. 

Phosphate  rock.     This  substance  has  already  been  mentioned 
under  insoluble  phosphate  of  lime.     Kock  phosphate  is  desig- 


Commercial  Fertilizers  165 

nated  usually  by  the  locality  from  which  it  is  obtained  as : — South 
Carolina  rock,  Florida  rock,  Tennessee  rock,  etc.  It  contains  25 
to  30  per  cent  of  phosphoric  acid  and  furnishes  the  chief  source 
of  the  supply  found  on  our  markets.  Apatite  is  a  purer  mineral 
phosphate  and  is  found  in  considerable  quantities  in  Canada, 
Norway,  Sweden  and  Spain.  Mention  has  already  been  made  of 
the  finely  ground  rock  phosphate  known  as  "floats."  Recent 
investigations  indicate  that  when  this  material  is  added  to  farm 
manure  it  has  a  high  fertilizing  value ;  in  fact  the  increased  crop 
production  at  the  Ohio  Experiment  Station,  due  to  adding  ground 
rock  phosphate  to  stall  manure  was  nearly  as  large  as  that  ob- 
tained from  the  addition  of  super-phosphate.  It  would  seem 
from  these  experiments  that  the  comparatively  inexpensive  floats 
might,  partially  at  least,  replace  super-phosphate,  if  used  in  con- 
nection with  manure  or  on  soils  rich  in  organic  matter.  The 
reason  usually  assigned  for  the  necessity  of  incorporating  this 
material  with  organic  matter,  is  that  the  latter  in  its  decay,  lib- 
erates acids,  which  attack  the  phosphate  and  render  it  more 
available. 

Bone  meal  or  ground  bone  is  a  product  of  the  packing  houses, 
glue  factories  and  soap  works,  the  raw  material  being  the  bones 
of  farm  animals.  These  are  either  ground  directly  (raw  bones) 
or  after  having  been  steamed  and  dried  (steamed  bones) .  This 
latter  process  removes  nearly  all  the  fat,  tendons  and  the  nitro- 
genous tissue  adhering  to  the  bones.  The  steamed  bone  which 
comes  from  the  glue  or  soap  factories,  is,  as  a  result  of  the  process 
of  steaming,  poorer  in  nitrogen  and  richer  in  phosphoric  acid 
than  the  raw  bones.  Raw  bone  contains  about  2.5  per  cent  of 
nitrogen  and  25  per  cent  of  phosphoric  acid,  while- the  average 
figures  for  steamed  bone  are  0.5  per  cent  and  29  per  cent  of 
nitrogen  and  phosphoric  acid,  respectively.  The  effect  of  bone 
meal  on  crops  is  largely  dependent  on  its  degree  of  fineness,  since 
it  will  be  decomposed  more  quickly  in  the  soil  the  finer  it  is 
ground.  Again,  the  raw  bone  meal  decomposes  more  slowly, 
due  to  the  presence  of  fat  which  retards  such  processes;  while 
the  steamed  bones  not  only  allow  a  much  more  perfect  pulveriza- 


166  Agricultural  Chemistry 

tion,  but  also  a  more  rapid  decomposition  in  the  soil,  and  conse- 
quently are  considered  of  somewhat  higher  availability.  Both 
materials  contain  the  phosphoric  acid  in  the  form  of  insoluble 
phosphate  of  lime. 

Bone  ash  is  incinerated  cattle  bones,  imported  from  South 
America;  the  nitrogenous  constituents  of  the  bones  have  been 
lost  in  the  process  of  burning.  It  consists  chiefly  of  the  insoluble 
phosphate  of  lime  and  contains  from  30  to  35  per  cent  of  phos- 
phoric acid.  Bone  black  or  animal  charcoal  is  a  refuse  product 
from  sugar  refineries  and  contains  about  33  per  cent  of  phos- 
phoric acid. 

Dissolved  bone  is  made  by  treating  raw  bone  with  sulphuric 
acid.  By  this  process  the  insoluble  phosphate  is  converted  into 
soluble  phosphate  and  the  organic  nitrogenous  material  into  sol- 
uble forms.  This  substance  contains  from  2  to  3  per  cent  of 
nitrogen  and  15  to  17  per  cent  of  available  phosphoric  acid.  •  It 
will  be  seen  that  in  respect  to  its  nitrogen  content  it  differs  ma- 
terially from  dissolved  rock  or  acid  phosphate,  which  does  not 
contain  this  element.  The  term  " dissolved  bone"  is  often  used 
in  speaking  of  "dissolved  rock,"  as  for  example,  "dissolved 
South  Carolina  bone."  This  use  of  the  term  is  incorrect,  as 
there  is  no  bone  in  South  Carolina  rock  phosphate. 

Basic  slag,  also  called  "Thomas  slag,"  or  "odorless  phos- 
phate," (CaO)r,P205Si02,  is  a  by-product  in  the  manufacture  of 
iron  and  steel  from  pig  iron  containing  phosphorus.  It  contains 
from  15  to  20  per  cent  of  phosphoric  acid  in  a  form  differing 
slightly  from  the  phosphates  already  discussed.  In  this  material 
there  are  five  parts  of  lime  combined  with  one  part  of  phosphoric 
acid  and  one  part  of  silica.  The  material  is  insoluble  in  water, 
but  readily  soluble  in  saline  solutions.  From  the  results  of 
numerous  experiments  it  has  been  found  that  this  material  has 
a  high  degree  of  availability,  about  equal  to  one-half  that  of  a 
soluble  phosphate.  Its  value  as  a  fertilizer  partly  depends  upon 
its  fineness  of  division.  The  finer  it  is  ground  the  more  quickly 
it  will  become  available.  The  fact  that  it  contains  a  high  lime 


Commercial  Fertilizers  167 

content  has  made  it  particularly  desirable  for  acid  soils,  on  which 
it  has  given  excellent  results. 

Guano.  Many  mixed  fertilizers  and  fertilizing  materials  are 
incorrectly  spoken  of  as  "guano."  The  term  should  be  applied 
to  the  natural  product  only,  which  consists  of  the  excrement  and 
remains  of  sea  fowls,  and  which  have  accumulated  in  certain  re- 
gions along  the  coast  of  South  America  and  on  some  of  the  islands 
in  the  Carribean  sea.  There  are  two  kinds,  dependent  upon  the 
conditions  under  which  they  were  formed.  When  the  formation 
took  place  in  a  dry  warm  region,  the  excrement  dried  quickly 
and  remained  practically  unchanged.  This  kind  will  contain  all 
the  nitrogen,  phosphoric  acid  and  potash  originally  in  the  man- 
ure. Some  of  the  early  guanos  contained  as  high  as  20  per  cent  of 
nitrogen,  but  those  now  on  the  market  are  of  poorer  quality  and 
contain  from  2  to  9  per  cent  of  nitrogen,  9  to  19  per  cent  of  phos- 
phoric acid  and  2  to  4  per  cent  of  potash.  Where  the  formation 
took  place  in  a  damp  climate,  then  fermentation  occurred, 
resulting  in  a  loss  of  nearly  all  of  the  organic  nitrogen.  If  much 
rain  fell,  there  was  also  a  loss  of  nearly  all  of  the  soluble  potash 
salts  and  soluble  phosphates.  This  has  produced  a  product  con- 
taining 15  to  30  per  cent  of  phosphoric  acid  in  the  form  of  in- 
soluble phosphates  of  lime,  iron  and  aluminum.  This  material 
is  generally  converted  into  a  soluble  phosphate  by  treatment 
with  sulphuric  acid,  before  reaching  the  market. 

Potash  fertilizers.  This  class  of  materials  is  generally  con- 
sidered of  relatively  less  importance  as  fertilizers  than  either  the- 
nitrogenous  or  phosphatic  fertilizers.  This  is  true  because  pot- 
ash compounds  are  usually  more  abundant  in  the  soil  than  either 
nitrogen  or  phosphoric  acid,  and  while  most  crops  remove  larger 
quantities  of  potash  than  of  phosphoric  acid,  the  former  is  more- 
likely  to  be  returned  to  the  soil.  It  has  already  been  stated  that 
potash  is  most  abundant  in  the  stems  and  leaves  of  plants,  and 
as  they  are  the  materials  generally  returned  to  the  land  in  the 
form  of  manure,  the  drain  from  the  soil  of  this  constituent  is 
therefore  much  less  than  in  the  case  of  the  nitrogen  and  phos- 
phoric acid.  Of  course,  when  the  whole  of  the  crop  is  removed 


168  Agricultural  Chemistry 

from  the  soil  the  loss  of  this  constituent  may  be  very  great. 
While  these  are  important  facts,  it  must  not  be  assumed  that  the 
addition  of  potash  fertilizers  is  unnecessary.  It  is  a  very  neces- 
sary constituent  of  fertilizers,  being  absolutely  essential  for  those 
intended  for  light,  sandy  soils,  and  for  peaty-meadow  lands,  as 
well  as  for  certain  potash-consuming  crops,  as  potatoes,  tobacco 
and  roots.  They  are  also  of  especial  value  for  clover,  grass,  corn 
and  fruits ;  they  should  be  applied  in  the  fall  on  heavy  clay  soils 
and  in  the  early  spring  on  sandy  soil.  The  former  soils  generally 
do  not  need  applications  of  potash  salts  as  much  as  sandy  soils, 
being  naturally  rich  in  this  fertilizer  ingredient. 

The  commercial  materials  on  the  market  are  muriate  of  pot- 
ash, sulphate  of  potash,  sulphate  of  potash  and  magnesia,  kainit, 
tobacco  stems  and  wood  ashes. 

Muriate  of  potash,  KC1,  is  manufactured  by  concentration 
from  the  crude  minerals  obtained  from  the  Stassfurt  mines  of 
Germany.  These  mines  of  Stassfurt  are  immense  saline  de- 
posits, formed  by  evaporation  of  large  inland  seas,  cut  off  from 
the  ocean  by  geological  changes.  These  deposits  are  the  main 
source  of  all  commercial  potash  fertilizers.  The  muriate  con- 
tains about  50  per  cent  of  potash,  all  of  which  is  combined  with 
chlorine.  At  the  present  price  per  ton  it  supplies  potash  at  a 
cheaper  price  per  pound  than  any  of  the  other  materials.  It 
can  be  used  on  all  soils  and  all  crops  except  a  few,  suck  as  to- 
bacco, potatoes  and  sugar  beets,  which  appear  to  be  injured  in 
quality  by  the  chlorine  present. 

Sulphate  of  potash,  K2S04.  This  is  another  concentrated 
product  of  the  Stassfurt  industry.  What  is  known  as  "high 
grade  sulphate"  contains  about  50  per  cent  of  potash  in  the  form 
of  sulphate.  A  low  grade  is  also  made,  which  contains  from  30 
to  35  per  cent  of  potash.  The  sulphate  of  potash  is  of  special 
value  for  those  crops  injured  by  chlorides,  as  mentioned  above. 

Sulphate  of  potash  and  magnesia,  MgS04.K2S04.6H,O.  This 
is  sometimes  called  "double  manure  salt."  It  is  obtained  from 
the  Stassfurt  mines,  and  contains  25  to  28  per  cent  of  potash. 
It  is  a  mixture  of  magnesium  sulphate  and  potassium  sulphate. 


Commercial  Fertilizers 


169 


Unless  the  cost  per  pound  of  actual  potash  in  this  material  is 
less  than  in  other  forms,  it  has  no  special  quality  to  recommend  it. 
Kainit,  K2S04.MgSO4MgCl,6H2O.  This  is  the  most  common 
product  of  the  Stassfurt  mines  and  is  a  mixture  of  various  salts. 
It  contains  from  12  to  14  per  cent  of  potash,  chiefly  in  the  form 
of  sulphate.  It  also  contains  a  considerable  quantity  of  com- 
mon salt,  some  chloride  and  sulphate  of  magnesium,  a  small 
quantity  of  gypsum  and  a  small  amount  of  potassium  chloride. 
It  is  a  low  grade  potash  salt  and  while  it  is  cheaper  per  ton,  the 


Potash  mines  at  Stassfurt,  Germany.     Mining  potash  for  fertilizers. 

actual  potash  costs  more  in  kainit  than  in  the  muriate  or  high 
grade  sulphate.  For  this  reason  it  is  not  desirable  to  purchase 
it  for  making  home  mixtures.  As  it  contains  chlorides  it  should 
not  1)e  used  as  a  fertilizing  material  for  tobacco,  potatoes,  or 
sugar  beets.  When  used  it  should  be  carefully  applied  to  the 
soil  so  that  it  will  not  come  in  contact  with  the  seed,  as  it  may 
seriously  interfere  with  germination. 


170  Agricultural  Cliemistry 

Tobacco  stems.  This  is  a  by-product  from  tobacco  factories. 
It  readily  undergoes  decomposition  in  the  soil,  its  potash  thus 
becoming  available.  It  contains  from  2  to  21/£  per  cent  of  nitro- 
gen, from  6  to  8  per  cent  of  potash  and  from  3  to  5  per  cent  of 
phosphoric  acid.  In  states  where  it  can  be  secured  at  a  com- 
paratively low  price,  it  can  be  used  very  profitably  in  making 
fertilizer  mixtures. 

Wood  ashes.  For  many  years  they  were  the  sole  source  of 
potash  for  fertilizing  purposes,  but  since  tha  introduction  of  the 
German  potash  salts,  there  is  less  of  this  material  found  on  the 
market.  They  are  valuable  when  unleached,  containing  in  this 
condition  from  2  to  8  per  cent  of  potash.  They  are  largely 
composed  of  carbonates  of  lime,  magnesia  and  potash,  with  a 
small  quantity  of  phosphates  (y2  per  cent).  The  ashes  from 
soft  woods  contain  less  potash  thf.n  those  from  hard  woods.  Coal 
ashes  have  practically  no  value  for  fertilizing  purposes.  Wood 
ashes  have  a  beneficial  action  on  the  mechanical  condition  of  light 
soils,  mainly  because  of  the  large  amount  of  lime  they  contain. 
This  binds  the  soil  particles  together,  thus  increasing  their  capil- 
lary action  and  improving  their  tilth.  On  clay  soils  there  is  a 
tendency  for  wood  ashes  to  cause  ' '  puddling. ' '  This  is  avoided 
by  applying  an  equal  quantity  of  land  plaster  with  the  ashes. 

All  the  materials  mentioned  with  the  exception  of  tobacco 
stems  are  soluble  in  water,  so  there  is  no  such  marked  difference 
in  availability  as  was  noted  in  the  case  of  nitrogenous  and  phos- 
phatic  fertilizers. 

Indirect  fertilizers.  There  are  a  number  of  substances  which 
are  beneficial  to  the  land  under  some  conditions,  although  they 
add  neither  humus  nor  important  quantities  of  plant  food. 
Among  such  materials  are  lime,  gypsum  and  common  salt. 

Lime,  CaO.  There  are  very  few  if  any  soils,  which  do  not 
contain  sufficient  lime  to  supply  the  plant.  The  chief  value  of 
lime  applications  must  be  as  an  indirect  fertilizer.  Its  action  is 
three-fold: — Mechanical,  chemical  and  biological.  Its  mechani- 
cal effect  on  heavy  soils  is  to  make  them  less  adhesive  and  more 


Commercial  Fertilizers  171 

friable  and  easier  to  work  when  dry.  On  light  porous  soils  its 
effect  is  exactly  the  reverse.  It  binds  the  particles  together,  in- 
creases the  cohesive  power  and  improves  capillarity.  Chemically, 
its  action  is  important.  It  acts  on  insoluble  potash  compounds, 
liberating  potash.  It  aids  in  the  decomposition  of  organic  mat- 
ter. It  corrects  acidity  by  combining  with  the  acids  present. 
Its  biological  action  is  dependent  upon  the  chemical  reactions 
it  induces.  Its  presence  is  a  necessary  condition  to  nitrification, 
a  biological  process.  It  combines  with  the  nitric  acid  formed, 
producing  nitrates.  By  maintaining  the  soil  neutral,  or  slightly 
alkaline,  it  creates  a  proper  medium  for  the  growth  and  de- 
velopment of  many  forms  of  micro-organisms,  which  are  so  nec- 
essary to  the  formation  of  available  plant  food. 

Lime  for  agricultural  purposes  is  put  upon  the  market  in 
several  different  forms: — as  caustic  lime,  CaO;  as  hydrate  of 
lime  or  water-slaked  lime,  Ca(OH)2;  as  air  slaked  lime  or  car- 
bonate of  lime,  CaC03 ;  as  ground  limestone  rock  and  as  ground 
oyster  or  clam  shells.  The  caustic  or  quick  lime  is  the  most 
concentrated  form  and  the  most  active.  It  is  made  up  of  the 
two  elements,  calcium  and  oxygen.  When  they  unite  we  have 
quick  lime,  or  calcium  oxide,  and  this  material  when  united  with 
carbon  dioxide  forms  calcium  carbonate,  CaC03,  the  chief  con- 
stituent of  limestone  and  oyster  and  clam  shells.  When  lime- 
stone is  burned  quick-lime  or  calcium  oxide  is  left  behind.  One 
hundred  pounds  of  pure  calcium  carbonate  will  yield  on  burn- 
ing 56  pounds  of  calcium  oxide,  and  44  pounds  of  carbon  dioxide 
will  be  driven  off.  From  the  quick  lime,  the  slaked  lime  is  ,ob- 
tained  by  addition  of  water  out  of  contact  with  the  air.  Fifty- 
six  pounds  of  caustic  become  76  pounds  of  slaked  lime.  When 
contact  of  air  is  allowed  the  56  pounds  of  caustic  become  100 
pounds  of  air  slaked  lime  by  again  combining  with  the  carbon 
dioxide  of  the  air.  Thus  it  will  be  seen  that  in  purchasing  lime 
it  will  be  more  economical  to  buy  the  caustic  or  quick  lime. 
However,  because  of  its  quick  action,  care  must  be  exercised  in  its 
use.  Finely  ground  limestone  is  coming  into  high  favor  and 
where  it  can  be  obtained  at  a  sufficiently  low  cost  is  undoubtedly 


172  Agricultural  Chemistry 

the  safest  form  to  use,  especially  by  the  inexperienced.  Lime 
should  be  applied  to  the  surface  and  if  possible  thoroughly  in- 
corporate with  the  few  upper  inches  of  the  soil.  The  clovers  and 
other  leguminous  plants  require  more  lime  than  do  the  cereals 
and  are  much  more  sensitive  to  acidity  of  the  soil.  A  good  stand 
of  clover,  therefore,  is  an  indication  that  the  soil  contains  suf- 
ficient lime. 

Gypsum  or  land  plaster,  CaS04.2H20,  is  a  sulphate  of  lime 
and  has  given  excellent  results  with  clover  and  other  leguminous 
plants.  It  is  now  generally  believed  that  its  beneficial  action  is 
due  to  the  fact  that  the  plaster  sets  free  the  unavailable  potash 
of  the  soil.  It  is  of  value  to  those  crops  that  are  benefited  by 
the  use  of  potash.  For  that  reason  it  gives  best  returns  when 
used  on  soils  rich  in  potential  potash,  as  the  clays,  with  practically 
no  beneficial  results  when  applied  to  sandy  soils.  Its  use  as  a 
source  of  sulphur  must  not  be  overlooked,  as  it  is  possible  that 
the  beneficial  results  obtained  in  many  cases  by  its  application 
will  have  to  be  traced  back  to  the  additional  supply  of  this  ele- 
ment. There  is  no  experimental  evidence  that  it  causes  soil 
acidity — a  statement  so  often  made. 

Salt,  NaCl,  has  sometimes  been  used  as  a  manure.  It  is  cer- 
tain that  in  special  cases  it  has  given  beneficial  results,  but  in 
other  instances  injury  has  resulted.  It  is  well  known  that  salt 
checks  fermentations  of  all  kinds  so  that  it  probably  influences 
the  rate  of  nitrification  going  on  in  the  soil.  It  is  said  that 
adding  salt  will  make  the  straw  of  wheat  stiffer,  but  this  effect 
is  probably  due  to  the  fact  that  salt  depresses  the  plant's  growth, 
making  the  straw  shorter  and  consequently  stiffer,  due  to  re- 
duced length.  It  may  also  by  mass  action  liberate  a  small 
amount  of  soluble  potassium  from  feldspathic  materials. 

Mixed  fertilizers.  The  tendency  of  the  fertilizer  trade  in  this 
country  has  been  toward  the  manufacture  and  sale  of  mixed 
fertilizers.  They  have  been  sold  in  the  form  known  as  complete 
fertilizers,  which  consist  of  a  mixture  of  two  or  more  of  the  basal 
materials  heretofore  described.  Where  the  basal  material  alone 


Commercial  Fertilizers  173 

is  richer  in  the  essential  ingredient  than  is  desired  by  the  manu- 
facturer, sufficient  gypsum,  dry  earth,  peat  or  other  inert  matter 
is  added  to  bring  the  percentage  of  these  ingredients  down  to  the 
desired  point.  Mixed  fertilizers  are  indiscriminately  recom- 
mended for  general  use  and  all  sorts  of  startling  claims  are  made 
for  them  by  the  manufacturers.  They  are  offered  as  universal 
fertilizers,  irrespective  of  the  well  known  fact  that  soils  differ 
widely  in  their  characteristics  and  that  the  crops  vary  in  their 
food  requirements.  So-called  special  fertilizers,  designed  for 
special  crops  and  supposed  to  be  adapted  to  their  particular  needs, 
are  common  on  the  market.  Some  manufacturers  offer  a  corn 
special,  a  potato  special,  a  tobacco  special,  etc.  Unfortunately 
their  chief  claim  lies  in  their  attractive  names.  The  science  of 
plant  nutrition  has  not  advanced  to  that  stage  where  one  can  de- 
fine what  the  minimum  of  essential  elements  necessary  for  the 
maximum  growth  of  the  plant  should  be.  And  even  if  we  had 
such  information,  the  makers  of  fertilizer  mixtures  entirely  dis- 
regard the  quantities  of  plant  food  already  existing  in  the  soil 
to  be  treated.  "When  the  farmer  studies  the  apparent  needs  of 
his  fields  and  understands  the  subject  of  fertilization  of  crops, 
he  will  prefer  to  buy  the  basal  fertilizing  materials  of  definite, 
known  composition  and  make  the  proportion  best  adapted  to  his 
needs,  rather  than  buy  mixed  fertilizers. 

High  and  low  grade  fertilizers.  As  the  basal  materials  used 
in  compounding  fertilizing  mixtures  differ  greatly  in  the  amounts 
of  plant  food  they  contain,  it  will  be  seen  that  products  made  by 
mixing  these  materials  will  contain  very  different  percentages  of 
nitrogen,  phosphoric  acid  and  potash.  If,  for  example,  dried 
blood,  bone  meal  and  muriate  of  potash  were  used,  the  fertilizer 
would  have  a  high  content  of  plant  food,  while  if  low  grade  tank- 
age, wood  ashes,  or  kainit  were  employed,  the  product  would 
have  a  low  percentage.  The  first  example  illustrates  a  high 
grade  product,  while  the  second  would  be  considered  as  low 
grade. 

As  the  low  grade  material  can  be  sold  at  a  comparatively  low 
price,  these  materials  find  a  ready  market,  although  the  plant 


174 


Agricultural  Chemistry 


food  in  the  cheap  fertilizer  actually  costs  more  per  pound.  This 
fact  is  clearly  brought  out  in  the  following  table  taken  from  a 
recent  bulletin  of  the  New  York  Experiment  Station  (Geneva). 

Average  Cost  of  One  Pound  of  Plant  Food  to  Consumers 


Nitrogen 

Phosphoric  Acid 

Potash 

Low  grade  complete 
fertilizer  

Cts. 
26.3 

Cts. 
8  0 

Cts. 
6  8 

Medium   grade   com- 
plete fertilizer  

23.2 

7.0 

6-0 

High  grade  complete 
fertilizer  

19  6 

6.0 

5.0 

Dried  blood  

18.5 

Nitrate  of  soda.  

13.9 

Acid  phosphate  

5.1 

Muriate  of  potash  .  .   . 

4.6 

It  will  be  seen  that  the  price  per  pound  of  plant  food  is  very 
much  less  in  high  grade  goods  than  in  low  grade  goods,  and  fur- 
ther, that  the  essential  elements  can  be  purchased  separately, 
more  cheaply  than  in  any  mixed  fertilizer. 

Home  mixing.  The  above  facts  emphasize  the  wisdom  of  the 
purchase  of  basal  materials  and  home  mixing.  The  difference  in 
cost  of  complete  fertilizers  and  the  basal  materials  per  pound  of 
plant  food  is  to  be  partly  attributed  to  the  expense  of  bagging 
and  mixing.  This,  Voorhees  has  shown  to  amount  to  about  $8.50 
per  ton.  That  this  practice  of  home  mixing  is  entirely  satisfac- 
tory has  been  abundantly  proven  by  the  Eastern  Experiment 
Stations.  It  allows  the  uniting  of  the  different  elements  in  the 
proportions  which  have  been  found  to  meet  best  the  requirements 
of  the  crop  and  the  soil  on  which  the  crop  is  to  be  raised.  By 
buying  the  basal  materials  separately  it  is  possible  to  apply  the 
different  elements  at  different  times.  This  point  may  be  of  great 
advantage  in  feeding  a  crop,  especially  one  needing  large  quan- 
tities of  nitrogen. 

The  conditions  and  materials  necessary  to  do  the  mixing  are 


Commercial  Fertilizers  175 

a  good,  tight  barn-floor,  or  a  dry,  smooth  earth- floor,  platform 
scales,  rake,  hoe,  shovel  and  screen. 

Selection  of  commercial  fertilizers.  It  is  impossible  to  give 
definite  directions  as*  to  the  kinds  and  quantities  of  fertilizers 
required  for  different  crops,  because  soils  differ  greatly  in  their 
total  content  of  plant  food,  and  we  have  no  direct  and  safe 
method  by  which  the  amounts  of  available  plant  food  can  be  ac- 
curately determined.  By  noting  carefully  the  growing  crops,  we 
may  get  in  a  general  way,  some  valuable  suggestions  as  to  which 
of  the  constituents  is  probably  lacking  in  a  soil.  For  instance, 
when  the  crop  has  a  deep  green  color,  with  well  developed  leaf 
and  stalk  and  luxuriant  growth,  it  may  be  assumed  that  the  soil 
is  not  deficient  in  nitrogen  and  potash.  A  rank  and  excessive 
growth  of  leaf  and  stem,  with  imperfect  bud  and  flower  develop- 
ment indicate  excessive  nitrogen  for  the  potash  and  phosphoric 
acid  present.  "When  grain  crops  tend  to  mature  early,  with  well 
defined,  well  developed,  plump  and  heavy  kernels,  there  will  be 
little  doubt  that  the  soil  contains  a  good  supply  of  available 
phosphoric  acid.  Potash  fertilizers  are,  generally  speaking,  of 
special  benefit  in  the  case  of  leafy  plants  like  tobacco,  cabbage, 
beets,  clover  and  potatoes.  While  some  help  may  be  had  from 
the  above  suggestions,  nevertheless  definite  methods  of  procedure 
have  been  proposed  by  several  investigators,  and  will  be  discussed 
briefly. 

Ville  system.  "The  system  which  has  perhaps  received  the 
most  attention,  doubtless  largely  because  one  of  the  first  pre- 
sented, and  in  a  very  attractive  manner,  is  the  one  advocated  by 
the  French  scientist,  George  Ville.  This  system,  while  not  to  be 
depended  upon  absolutely,  suggests  lines  of  practice  which,  un- 
der proper  restrictions,  may  be  of  very  great  service.  In  brief, 
this  method  assumes  that  plants  may  be,  so  far  as  their  fertiliza- 
tion is  concerned,  divided  into  three  distinct  groups.  One  group 
is  specifically  benefited  by  nitrogenous  fertilization,  the  second 
by  phosphatic,  and  the  third  by  potassic.  That  is,  in  each  class 
or  group,  one  element  more  than  any  other  rules  or  dominates 


176  Agricultural  Chemistry 

the  growth  of  that  group,  and  hence  each  particular  element 
should  be  applied  in  excess  to  the  class  of 'plants  for  which  it  is  a 
dominant  ingredient.  In  this  system  it  is  asserted  that  nitrogen 
is  the  dominant  ingredient  for  wheat,  rye,  'oats,  barley,  meadow 
grass  and  beet  crops.  Phosphoric  acid  is  the  dominant  fertilizer 
ingredient  for  turnips,  Sivedes,  Indian  corn,  (maize),  sorghum, 
and  sugar  cane;  and  potash  is  the  dominant  or  ruling  element 
for  peas,  beans,  clover,  vetches,  flax,  and  potatoes.  It  must  not 
be  understood  that  this  system  advocates  only  single  elements, 
for  the  others  are  quite  as  important  up  to  a  certain  point,  be- 
yond which  they  do  not  exercise  a  controlling  influence  in  the 
manures  for  the  crops  of  the  three  classes.  This  special  or  dom- 
inating element  is  used  in  greater  proportion  than  the  others, 
and  if  soils  are  in  a  high  state  of  cultivation,  or  have  been  ma- 
nured with  natural  products,  as  stable  manure,  they  may  be  used 
singly  to  force  a  maximum  growth  of  the  crop.  Thus,  a  specific 
fertilization  is  arranged  for  the  various  rotations,  the  crop  re- 
ceiving that  which  is  the  most  useful.  There  is  no  doubt  that 
there  is  a  good  scientific  basis  for  this  system,  and  that  it  will 
work  well,  particularly  where  there  is  a  reasonable  abundance 
of  all  the  plant  food  constituents,  and  where  the  mechanical  and 
physical  qualities  of  the  soil  are  good,  though  its  best  use  is  in 
'intensive'  systems  of  practice.  It  cannot  be  depended  upon  to 
give  good  results  ivhere  the  land  is  naturally  poor,  or  run  down, 
and  where  the  physical  character  also  needs  improvement." 

Wagner  system.  ''Another  system  which  has  been  urged, 
notably  by  the  German  scientist,  Wagner,  is  based  upon  the  fact 
that  the  mineral  constituents,  phosphoric  acid  and  potash,  form 
fixed  compounds  in  the  soil  and  are,  therefore,  not  likely  to  be 
leached  out,  provided  the  land  is  continuously  cropped.  They 
remain  in  the  soil  until  used  by  growing  plants,  while  the  nitro- 
gen, on  the  other  hand,  since  it  forms  no  fixed  compounds  and 
is  perfectly  soluble  when  in  a  form  useful  to  plants,  is  liable  to 
loss  from  leaching.  Furthermore,  the  mineral  elements  are  rel- 
atively cheap,  while  the  nitrogen  is  relatively  expensive,  and  the 
economical  use  of  this  expensive  element,  nitrogen,  is  dependent 


Commercial  Fertilizers  177 

to  a  large  degree  upon  the  abundance  of  the  mineral  elements 
in  the  soil.  It  is,  therefore,  advocated  that  for  all  crops  and  for 
all  soils  that  are  in  a  good  state  of  cultivation,  a  reasonable  ex- 
cess of  phosphoric  acid  and  potash  shall  be  applied,  sufficient  to 
more  than  satisfy  the  maximum  needs  of  any  crop,  and  that  the 
nitrogen  be  applied  in  active  forms,  as  nitrate  or  ammonia,  and 
in  such  quantities  and  at  such  times  as  will  insure  the  minimum 
loss  of  the  element  and  the  maximum  development  of  the  plant. 
The  supply  of  the  mineral  elements  may  be  drawn  from  the 
cheaper  materials,  as  ground  bone,  tankage,  ground  phosphates 
and  iron  phosphates,  as  their  tendency  is  to  improve  in  character ; 
potash  may  come  from  the  crude  salts.  Nitrogen  should  be  ap- 
plied as  nitrate  of  soda,  because  in  this  form  it  is  immediately 
useful,  and  thus  may  be  applied  in  fractional  amounts,  and  at 
such  times  as  to  best  meet  the  needs  of  the  plant  at  its  different 
stages  of  growth,  with  a  reasonable  certainty  of  a  maximum  use 
by  the  plant.  Thus  no  unknown  conditions  of  availability  are 
involved,  and  when  the  nitrogen  is  so  applied,  the  danger  of  loss 
by  leaching,  which  would  exist  if  it  were  all  applied  at  one  time, 
is  obviated." — (Voorhees.) 

System  based  on  the  analysis  of  the  plant.  "Still  another 
system  is  based  on  the  food  requirements  of  the  plant  as  shown 
by  the  analysis  of  the  plant  itself.  The  amount  of  plant  food 
removed  from  each  acre  of  ground  is  calculated  from  the  analysis 
of  the  plant  and  a  corresponding  amount  is  returned  to  the  soil. 
Different  formulas  are,  therefore,  recommended  for  each  crop, 
and  in  these  the  nitrogen,  phosphoric  acid  and  potash  are  com- 
bined in  the  same  proportions  in  which  they  are  found  in  the 
plant.  Experience  shows  that  it  is  necessary  to  add  amounts  of 
these  fertilizers  to  the  soil  that  will  supply  more  plant  food  than 
is  removed  by  the  crop  if  the  maximum  results  are  desired.  This 
system  may  result  in  a  large  yield,  but  cannot  be  considered  an 
economical  method  of  feeding  the  plant,  as  one  or  more  of  the 
elements  is  likely  to  be  applied  in  excess  of  the  requirements  of 
the  crop.  It  does  not  take  into  consideration,  for  instance,  the 
fact  that  a  plant  which  contains  a  large  amount  of  one  element 


178  Agricultural  Chemistry 

of  plant  food  may  possess  unusually  great  power  of  procuring 
that  element  from  the  soil.  The  principle  underlying  this  sys- 
tem, of  course,  is  the  idea  that  to  maintain  the  fertility  of  the 
soil  unimpaired  an  amount  of  plant  food  equivalent  to  that  re- 
moved by  the  crop  must  be  returned  to  the  land.  To  this  extent 
the  system  is  simliar  to  the  use  of  barnyard  manure,  but  is  not 
so  effective." 

Money  crop  system.  "Another  system  used  in  ordinary  or 
extensive  farming  is  to  apply  all  the  fertilizer  to  the  money  crop 
of  the  rotation.  This  method  is  used  especially  where  only  one 
crop  in  a  rotation  is  sold,  the  others  being  fed  on  the  farm.  A 
liberal  supply  of  food  is  used  to  give  the  maximum  yield  which 
the  climate  and  season  will  permit.  The  amount  of  food  applied 
is  in  excess  of  the  requirements  of  the  crop  and  the  residue  is 
depended  upon  to  help  nourish  the  succeeding  crops,  or  at  least 
the  one  immediately  succeeding  the  money  crop.  This  system 
has  some  valuable  features  and  is  probably  the  one  most  in  use 
in  this  country  at  the  present  time. 

"Too  frequently  fertilizers  are  used  by  what  certain  writers 
have  called  the  '  hit  or  miss '  system.  No  special  thought  is  given 
to  the  requirements  of  the  crop  or  the  composition  of  the  fer- 
tilizer, but  if  a  farmer  feels  that  he  can  afford  it  and  the  agent 
is  a  glib  talker,  the  sale  is  made.  If  the  buyer  happens  to  'hit' 
the  food  requirements  of  his  crop  a  profit  is  secured  and  he  is 
correspondingly  happy,  while  if  he  makes  a ''miss'  he  feels  as- 
sured that  there  is  no  value  in  commercial  fertilizers. " — (Vivian.) 

Field  experiments  necessary.  These  systems  described  have 
their  good  features,  but  they  do  not  take  into  account  the  import- 
ant fact  that  soils  differ  greatly  in  the  amount  and  availability  of 
the  plant  food  they  already  "contain.  In  order  to  determine  with 
any  degree  of  certainty  what  particular  constituents  are  needed 
the  farmer  must  conduct  some  experiments  for  himself.  This 
can  be  done  by  carefully  marking  off  certain  portions  of  the  field, 
of  definite  size  and  uniform  soil,  and  using  on  them  different 
fertilizing  materials.  Plots  one  rod  wide  and  8  rods  long,  and 


Commercial  Fertilizers 


179 


containing  1/20  of  an  acre,  are  of  convenient  size.  The  table  on 
this  page  shows  the  arrangement  and  kinds  and  quantity  of  ma- 
terials to  be  used  on  each  plot. 

Plan  for  Plot  Experiments  with  Fertilizers 


Plot  No. 

Plant  Food  Applied 

1. 

None. 

2. 

N. 

Dried  blood—  30  Ibs. 

3. 

P. 

Steamed  bone  meal  —  10  Ibs. 

4. 

S. 

Calcium  sulphate—  10  Ibs. 

5. 

K. 

Potassium  chloride  —  10  Ibs. 

6. 

None. 

7. 

N.  &P. 

Blood  and  bone. 

8. 

N.  &S. 

Blood  and  sulphate. 

9. 

P.  &S. 

Bone  'and  sulphate. 

10. 

P.  &  K. 

Bone  and  chloride. 

11. 

N.  P.  &  S. 

Blood,  bone  and  sulphate. 

12. 

N.  P.  S.  K. 

Blood,  bone,  sulphate  and  chloride. 

13. 

None. 

Careful  notes  should  be  made  during  the  growing  period  and 
at  the  end  of  the  growing  season  and  when  the  crop  is  harvested 
comparison  made  as  to  the  yields  by  weight  obtained.  In  this 
way  definite  information  will  be  secured  as  to  whether  the  soil 
is  lacking  in  one  or  two,  or  all  three  of  the  constituents  of  plant 
food  in  available  form.  In  carrying  out  field  tests  such  as  these 
it  should  be  borne  in  mind  that  the  results  of  one  year's  work 
are  not  perfectly  reliable,  since  prevailing  weather  conditions, 
as  well  as  other  factors,  may  produce  very  different  results.  It 
will  be  well  to  continue  the  work  for  several  years  in  order  to 
eliminate  any  differences  due  to  differences  of  season. 

It  must  also  be  remembered  that  the  requirements  for  different 
crops  will  vary.  By  carrying  the  plots  through  several  seasons 
and  using  the  rotation  common  for  that  particular  farm,  the 
special  crop  needs  can  also  be  ascertained.  When  the  needs  of 
the  soil  and  crop  have  been  established  the  cheapest  sources  of 
the  necessary  materials  should  be  employed. 


180  Agricultural  Chemistry 

Amount  of  fertilizers  to  be  applied.  No  definite  rules  can  be 
given  as  to  the  quantities  of  commercial  fertilizers  to  be  applied, 
for  the  amount  necessary  to  produce  large  crops  will  vary  with 
the  character  and  state  of  fertility  of  the  soil,  the  kind  of  crop 
to  be  grown,  the  time  and  manner  of  application  and  many  other 
factors.  Five  hundred  pounds  per  acre  may  be  considered  a 
heavy  application  for  ordinary  farm  crops ;  applications  of  more 
than  that  amount  will  only  give  economical  returns  in  the  case 
of  special  crops  grown  under  an  intensive  system  of  farming. 
Heavy  applications  at  long  intervals  are  not  as  productive  of 
good  results  as  light  applications  more  frequently.  It  is  better 
not  to  make  applications  of  over  200  pounds  per  acre  of  any  one 
basal  material  and  to  vary  the  amount  from  year  to  year  until 
experience  has  shown  that  economical  returns  can  be  expected  by 
heavier  applications.  Lime  may  be  applied  at  the  rate  of  1000 
pounds  per  acre  on  light  soils  and  double  that  amount  on  heavy 
soils.  This  application  once  in  5  or  6  years  is  usually  sufficient. 

Fertilizer  laws  and  guarantees.  To  protect  the  farmer  against 
the  sale  of  fraudulent  and  spurious  goods,  the  manufacturers  are 
compelled  by  law  in  most  states,  to  give  the  actual  amounts  of 
the  different  constituents  contained  in  their  products.  Usually 
they  are  compelled  by  law  to  state  on  each  bag  or  parcel  offered 
for  sale  the  percentage  of  nitrogen  (or  ammonia),  available  phos- 
phoric acid  and  potash.  The  enforcement  of  the  law  and  the  chem- 
ical examination  of  the  fertilizers  to  determine  if  they  agree  with 
the  guarantee,  rests  with  the  State  Experiment  Station,  or  in 
some  states  with  the  State  Department  of  Agriculture.  The 
results  secured  are  published  in  bulletins  available  to  the  farmers 
of  the  state,  and  should  be  consulted  freely  by  those  buying 
such  materials.  These  laws  have  resulted  in  almost  complete 
disappearance  of  materials  compounded  with  the  intention  of 
defrauding,  as  well  as  a  great  lessening  in  the  number  of  brands 
offered  for  sale.  Nevertheless,  statements  often  appear  on  the 
bags,  which,  to  say  the  least,  are  confusing  and  may  mislead  the 
buyer.  Phosphoric  acid  10  per  cent,  for  example  is  often  stated 
as  equivalent  to  bone  phosphate,  22  per  cent.  To  the  buyer  the 


Commercial  Fertilizers  181 

higher  figure  is  attractive  and  he  is  led  to  believe  that  he  will 
obtain  something  more  than  the  10  per  cent  of  phosphoric  acid 
guaranteed.  The  following  example,  taken  from  the  label  of  a 
fertilizer  bag,  will  explain  this  point  more  fully : — 

GENERAL  CROP  BRAND. 

Guaranteed  Analysis. 

Nitrogen,  N    0.82 —  1.65  per  cent 

Ammonia,  NHg 1.0  —  2.0           " 

Available  Phosphoric  Acid,  P2O5  8.0  —10.0 

Equal  Bone  Phosphate,  Ca3(PO^)2 17.0  —21.0 

Total  Phosphoric  Acid,  P2O5   10.0  —1.2.0           " 

Potash  Sulphate,  K2SO4  . . .  ? 11.0  —13.0 

Potash,    K2O    2 6.0  —  7.0           " 

Color  not  guaranteed. 

The  buyer  is  only  concerned  in  the  total  amount  of  nitrogen, 
available  phosphoric  acid  and  potash  that  the  brand  contains, 
and  these  figures  alone  should  dictate  the  actual  worth  of  the 
material. 


CHAPTER  VIII 
CROPS 

Having  considered  somewhat  in  detail  the  chemical  composi- 
tion of  plants  and  the  functions  of  the  chemical  elements  con- 
cerned in  their  growth,  we  are  in  a  position  to  discuss  in  general 
terms  the  relative  composition  and  food  requirements  of  crops, 
and  the  factors  influencing  their  composition  and  feeding  value. 
For  the  sake  of  convenience,  the  common  crops  will  be  considered 
under  the  following  arbitrary  divisions : — 

I.  Seed  crops — including, 

a.  Cereal  grains,  such  as  wheat,  corn,  rye,  barley,  oats 

and  rice. 

b.  Leguminous  seeds,  such  as  beans,  peas,  cowpeas  and 

soy  beans. 

c.  Miscellaneous  seeds,  such  as  cotton  seed,  flaxseed,  cas- 

tor beans  and  others. 
II.  Hay  or  fodder  crops — including, 

a.  Common  grasses,  such  as  timothy,  red  top  and  Ken- 

tucky blue  grass. 

b.  Cereal  plants,  such  as  corn,  oats,  barley  and  other  crops, 

cut  at  an  immature  stage  for  soiling  purposes,  sil- 
age, or  hay. 

c.  Leguminous  crops,  such  as  alfalfa  and  the  various  clov- 

ers  (which  form  true  hays),  and  the  pea,  cowpea, 
vetch  and  soy  bean  (when  cut  green  for  soiling  pur- 
poses or  for  curing  as  hays). 
III.  Root  crops — including, 

a.  True  roots,  such  as  mangels,  turnips,  beets  and  carrots. 

b.  Tubers,  or  subterranean  stems,  such  as  potatoes. 


Crops  183 

IV.  Fruit  crops — including, 

a.  Fruit  of  perennial  plants,  such  as  the  apple,  pear,  plum, 

peach,  grape  and  most  berries,  as  well  as  the  orange 
lemon,  banana  and  other  tropical  fruits. 

b.  Fruit   of   annual   plants — such   as  melons,   pumpkin, 

squash  and  tomato. 
V.  Forest  growth — including, 

hardwooded  and  softwooded  perennial  plants. 
VI.  Miscellaneous  crops — including, 

tobacco,  and  the  onion,  cabbage,  and  other  truck  crops.  , 

In  considering  the  seed  crops  we  must  take  into  account  the 
straw  as  well  as  the  grain.  The  former  portion  of  these  crops 
is  not  important  in  all  cases  as  a  feeding  material,  but  it  always 
stands  responsible  for  a  part  of  the  exhaustion  of  plant  food 
from  the  soil.  For  this  reason  the  tops  as  well  as  the  roots  of 
root-crops  should  be  considered. 

The  yield  of  crops,  both  in  the  total  substance  produced  and! 
in  its  proportion  of  plant  compounds,  varies  widely.  These  fac- 
tors control  to  a  large  extent  the  value  of  the  crops  as  feeding- 
stuffs,  and  their  demands  upon  the  plant  food  constituents  of 
the  soil.  A  rational  comparison  of  the  composition  of  crops  can 
be  made  only  upon  the  basis  of  yield  of  dry  matter  and  of  the 
individual  nutrient  compounds  or  groups  of  compounds  con- 
tained therein,  per  acre.  The  table  on  page  184  gives  the  total 
yields  and  the  yields  of  proximate  constituents  of  such  compara- 
ble amounts  of  crops. 

The  differences  between  weights  of  fresh  material  and  of  dry 
matter  in  this  table  are  due  almost  entirely  to  water  lost 
in  the  process  of  complete  curing  or  drying.  For  example,  corn 
in  the  green  state  consists  of  nearly  80  per  cent  of  water,  pota- 
tces  have  about  the  same  amount,  sugar  beets  contain  about  86 
per  cent,  and  mangels  consist  of  over  90  per  cent  of  this  constitu- 
ent. The  several  hay  crops  of  the  following  table  are  rather 
lower  in  water,  containing  from  60  to  a  little  over  70  per  cent. 


Agricultural  Chemistry 


This  amount  is  greatly  reduced  by  the  curing  process  so  that  the 
hays  contain  only  from  10  to  20  per  cent. 

The  field  cured  grain  crops  carry  from  7  to  9  per  cent  of 
moisture  in  the  straw  and  about  11  per  cent  in  the  seed.  The 
high  water  content  of  some  of  these  crops,  aside  from  its  detri- 
mental effect  upon  keeping  qualities,  is  sometimes  of  importance 

Yield  in  Pounds  Per  Acre 


Fresh 
material 

Dry 
matter 

Crude 
protein 

N.  free 
extract 

Ether 
extract 

Crude 
fiber 

Ash 

Alfalfa  

35,  000 

9,870 

1,680 

4,305 

350 

2,590 

045 

Corn  .  .       

30,  000 

6,270 

510 

3,300 

240 

1,800 

4'?0 

Red  clover  

18,000 

5,256 

792 

2,430 

198 

1,458 

378 

Timothy  

11,500 

4,416 

356 

2,323 

138 

1,357 

?31 

Hungarian  grass.  .  . 
Mangels  

19,000 
60  000 

3,591 
5,400 

589 
840 

2,698 
3,300 

133 
120 

1,748 
540 

323 
(560 

Sugar  beets  

32,000 

4,320 

570 

3,136 

32 

288 

l>88 

Potatoes  

18,000 

3,798 

378 

3,114 

18 

104 

180 

Oats  

1,120 

995 

132 

668 

56 

106 

33 

Oat  straw  

4,000 

3,672 

160 

1,696 

92 

1,480 

<>04 

Barley  

1,200 

1,069 

147 

837 

21 

32 

?8 

Barley  straw  

4,  OUO 

3,432 

140 

1,560 

60 

1,400 

?,?,S 

Cabbage  

18,  460 

4,800 

1,200 

1,900 

200 

751 

700 

Tobacco  (leaf)  

12,  340 

1,730 

300 

935 

51 

263 

321 

with  reference  to  economy  of  transportation.  For  example,  since 
the  root  crops  retain  most  of  their  original  water  content  during 
proper  storage,  it  is  evident  that  a  given  amount  of  dry  food 
material  is  handled  far  less  economically  in  them  than  in  grains 
and  hays.  It  will  be  observed  that  the  enormous  acre-yields  of 
these  crops,  particularly  of  the  mangel,  are  reduced  to  moderate 
figures  when  considered  in  terms  of  dry  matter. 

The  high  protein  content  of  the  legume  hays  (clover  and  al- 
falfa) is  in  marked  contrast  to  the  amount  of  this  group  of  con- 
stituents in  the  common  hays  and  the  cereal  crops.  This  differ- 
ence will  be  discussed  in  detail  in  the  consideration  of  individual 
crops.  Mangels  also  contain  a  high  percentage  of  "crude  pro- 


Crops  185 

tein;"  but  it  has  been  shown  that  more  than  one-half  of  the  ni- 
trogen upon  which  this  figure  is  based  is  not  in  the  form  of  pro- 
tein but  is  contained  in  amide  or  amino  acid  compounds.  This 
is  probably  true  for  other  root  crops,  and  greatly  diminishes 
their  apparent  protein  value. 

With  reference  to  the  production  of  fat,  it  should  be  stated 
that  while  the  grains  may  yield  quite  pure  fats  to  the  chemist's 
method  of  analysis,  this  will  be  far  from  true  in  the  case  of  hays 
and  straws.  Considerable  amounts  of  chlorophyll  will  contam- 
inate the  ' '  crude  fats ' '  determined  for  the  hay  crops.  The  high 
yield  of  ether  extract  in  alfalfa  hay,  as  in  the  case  of  other  con- 
stituents of  this  crop,  is  incident  to  a  large  total  yield  of  dry 
matter  obtained  from  the  several  successive  cuttings  per  season. 
In  this  respect,  this  crop  possesses  a  marked  advantage  in  com- 
parison with  the  others. 

A  large  proportion  of  the  ash  of  cereal  straws,  some  of  the 
cereal  grains,  and  the  common  hays,  consists  of  non-essential 
silica.  The  legumes  and  root-crops  in  general,  however,  are  very 
low  in  this  constituent.  The  excessive  ash  content  of  alfalfa,  the 
mangel,  the  cabbage  and  other  crops  is  notable ;  being  composed 
chiefly  of  such  essential  constituents  as  lime,  potash,  and  phos- 
phoric acid,  it  has  a  significant  bearing  upon  the  well-known  ex- 
haustive effects  of  these  crops  upon  the  soil.  A  knowledge  of  the 
amount  and  composition  of  the  ash  of  crops  gives  a  basis  for  the 
selection  of  animal  rations,  well-balanced  in  ash  constituents. 

The  relative  drain  of  some  crops  upon  the  soil  is  shown  by  the 
last  table  in  the  appendix,  quoted  from  Warington.  The  figures 
for  sulphur  trioxide  have  been  corrected  in  most  cases  on  the  basis 
of  determinations  made  at  the  Wisconsin  Experiment  Station. 
The  older  determinations  of  sulphur  by  analysis  of  the  ash  have 
been  shown  to  be  low.  Other  data  have  been  compiled  from  vari- 
ous sources  and  added  to  Warington 's  table. 

The  food  requirements  of  cereal  grains,  as  shown  by  a  gen- 
eral survey  of  the  table,  are  not  widely  variant.  It  will  be  ob- 
served that  the  ash  constituents  are  uniformly  much  higher  in 


186  Agricultural  Chemistry 

the  straw  than  in  the  grain.  Nitrogen,  on  the  other  hand,  ac- 
cumulates chiefly  in  the  grain,  about  two-thirds  of  the  total  ni- 
trogen removed  being  found  in  this  part  of  the  crop.  The  sep- 
arate constituents  of  the  ash  show  great  differences  in  their 
relative  distribution  between  grain  and  straw.  Thus,  while  pot- 
ash, soda,  lime,  chlorine  and  silica  are  located  chiefly  in  the 
straw,  the  greater  part  of  the  phosphoric  acid  occurs  without 
exception  in  the  grain;  sulphur  trioxide  and  magnesia  are  quite 
evenly  divided  between  the  two  parts  of  the  crop. 

Nitrogen  and  phosphoric  acid  are  probably  the  plant  food  con- 
stituents most  frequently  lacking  in  soils  and  in  many  cases  their 
depletion  is  to  be  attributed  to  continuous  raising  and  selling  of 
grain  crops.  It  is  evident  that  either  the  manure  from  grains 
fed  on  the  farm  should  be  carefully  husbanded,  or  equivalent  re- 
turns of  plant  food  to  the  farm  should  be  made  by  the  purchase 
of  feeding  stuffs  or  fertilizers.  This  subject  has  been  fully  dis- 
cussed in  the  chapter  on  Farm  Manure.  It  applies  with  particu- 
lar emphasis  to  cereal  crops,  because  they  are  wholly  dependent 
upon  stores  of  available  nitrogen  in  the  soil  for  their  supply  of 
this  element  and  generally  thrive  best  when  supplied  with  avail- 
able forms  of  phosphoric  acid. 

The  conservation  of  the  smaller  amounts  of  plant  food  in  cereal 
straws  likewise  should  not  be  neglected.  The  practice  of  dis- 
posing of  these  straws  by  burning  is  a  wasteful  one,  for  by  this 
treatment  the  nitrogen  which  they  contain  is  entirely  lost. 

Food  requirements  of  the  common  grasses.  The  common 
hays,  represented  in  our  table  by  meadow  hay,  are  essentially 
straw  crops,  and  their  food  requirements  practically  duplicate 
those  of  the  cereal  crops.  Hays  of  the  legumes  show  marked 
differences  from  the  true  hays.  While  for  example,  clover  hay 
removes  twice  as  much  nitrogen  from  the  land  as  do  the  cereal 
crops  or  meadow  liay,  it  should  be  borne  in  mind  that,  like  other 
legumes,  this  crop  obtains  almost  all  its  nitrogen  from  the  air 
through  the  activity  of  bacteria  living  in  association  with  its 


Crops 

roots.     As  will  be  demonstrated  further  on,  these  crops  increase 
rather  than  diminish  the  supply  of  nitrogen  in  the  soil. 

The  true  legume  hays  develop  extensive  root  systems  and  draw 
heavily  upon  the  ash  constituents  of  the  soil.  This  applies  in  a 
limited  degree  to  phosphoric  acid,  but  more  particularly  to  potash 
and  lime,  which  form  one-half  the  total  ash  of  the  bean  crop,  two 
thirds  of  the  ash  of  clover  hay,  and  nearly  as  large  a  proportion 
in  the  case  of  alfalfa  hay.  The  legume  family  of  plants,  par- 
ticularly the  clovers  and  alfalfa,  is  especially  sensitive  to  acid 
conditions  of  the  soil.  This  is  probably  because  such  a  medium 
is  unfavorable  for  the  activity  of  nitrogen-fixing  bacteria.  This 
condition  cannot  develop  in  a  soil  properly  stocked  with  lime. 

The  leguminous  grain  crops  such  as  beans  or  peas  are  less  ex- 
hausting to  the  minerals  of  the  soil  than  are  the  hays  of  legumes, 
for  they  develop  a  less  extensive  root  system.  These  crops  show 
the  same  general  distribution  of  constituents  between  the  grain 
and  straw  as  do  the  cereal  crops,  and,  as  with  the  latter  crops, 
the  greater  part  of  the  nitrogen  and  phosphoric  acid  is  removed 
in  the  seed. 

Requirements  of  root  crops.  The  true  root  crops  are  pre- 
eminently soil-exhausting  crops.  Not  only  do  they  assimilate 
greater  amounts  of  ash  constituents  per  acre  than  the  other  crops 
removed  from  the  soil,  with  the  exception  of  alfalfa,  but  they 
remove  more  nitrogen  than  the  cereals  or  grasses.  In  the  case 
of  turnips,  this  amount  of  nitrogen  is  seen  to  be  twice  that  re- 
moved by  cereal  grains  or  meadow  hay,  and  in  the  case  of  man- 
gels, it  is  three  times  as  much  as  these  crops  contain.  It  is 
important  to  realize  that  the  root  crops  are  entirely  dependent 
upon  the  soil  for  this  important  element  of  plant  food.  Potash 
is  uniformly  conspicuous  for  its  high  proportion  in  the  ash  of 
these  crops.  Its  presence  is  explained  by  the  fact  already  ob- 
served, that  this  mineral  is  essential  to  the  production  of  starch 
and  sugar,  which  are  predominant  compounds  in  these  crops. 
Since  the  amounts  of  phosphoric  acid  removed  by  these  crops  are 
also  uniformly  high,  it  is  apparent,  as  demonstrated  also  by  prac- 


188  Agricultural  Chemistry 

tioe,  that  they  require  especially  complete  and  heavy  manuring 
when  grown  under  intensive  cultivation. 

Requirements  of  fruit  crops.  This  class  of  crops  is  less  ex- 
haustive and  less  dependent  upon  immediate  manuring  than  the 
crops  already  discussed;  the  individual  requirements  will  be 
considered  later. 

Requirements  of  forest  growth.  Timber  growth  exceeds  most 
of  the  other  crops  discussed  in  the  annual  production  of  dry 
matter,  but  this  increase  is  obtained  at  small  expense  in  plant 
food.  According  to  Warington,  the  production  of  3000  pounds 
of  dry  pine  timber  requires  the  consumption  of  only  2.5  pounds 
of  potash  and  1  pound  of  phosphoric  acid  per  acre  yearly. 
Harder  woods  require  rather  more  of  these  constituents.  The 
amount  of  nitrogen  in  wood  is  very  small,  amounting  to  an  aver- 
age of  about  10  pounds  for  an  annual  growth  of  beech  wood. 
Trees  produce  seed  only  at  mature  age  and  then  at  the  expense 
of  material  stored  in  the  leaves  and  wood. 

The  litter  which  accumulates  during  the  earlier  years  of 
growth  will  therefore  be  most  effective  in  increasing  the  value  of 
the  surface  soil  by  stores  of  plant  food  obtained  from  the  deeper 
soil  layers.  As  a  result  of  this  process,  the  manurial  require- 
ments of  the  forest  are  low  and  become  much  smaller  than  in 
ordinary  cropping. 

Requirements  of  truck  crops.  The  various  truck  crops  differ 
widely  in  productiveness  and  feeding  habits.  Of  the  more  im- 
portant ones,  the  cabbage  assimilates  large  amounts  of  ash  con- 
stituents, with  the  exception  of  silica  while  the  tobacco  crop  is  a 
comparatively  light  feeder.  The  heavy  yield  desired  with  such 
crops  entails  a  correspondingly  high  consumption  of  nitrogen 
and  necessitates  heavy  manuring  with  this  element,  as  well  as 
liberal  manuring  with  potash  and  phosphoric  acid.  The  high 
content  of  sulphur  tri-oxide  in  this  crop  and  in  the  turnip  and 
other  members  of  the  cruciferae,  suggests  that  in  some  cases  this 
element  may  become  the  limiting  factor  in  plant  growth,  and 
that  the  beneficial  effects  sometimes  observed  from  the  applica- 


Crops  189 

tion  of  gypsum  may  be  due  to  the  sulphur  tri-oxide  which  it 
supplies. 

Crop  residues,  which  include  the  leaves  of  root  crops,  the 
straws  of  grain  crops,  the  stalks  of  tobacco  and  waste  parts  from 
trimming,  contain  sufficient  plant  food  to  justify  the  exercise  of 
care  to  return  them  to  the  soil.  Potash  and  lime  are  the  con- 
stituents of  most  concern  in  the  straws  and  they  are  of  even 
greater  consequence  in  the  leaves  of  root  crops.  The  common 
practice  of  spreading  tobacco  stalks  to  decay  upon  the  land, 
makes  possible,  as  indicated  by  the  last  table  in  the  appendix, 
the  returning  of  considerable  amounts  of  potash  and  also  of  ni- 
trogen to  the  soil.  These  crop  residues  are  frequently  reduced 
to  ashes  to  economize  labor  in  their  disposal,  but  this  practice 
should  be  discouraged,  since  it  involves  a  loss  of  much  nitrogen. 

Whenever  the  soil  will  profit  by  the  addition  of  organic  mat- 
ter, these  materials  should  be  turned  in  whole.  Another  prac- 
tice, much  better  than  burning,  is  to  compost  such  material  with 
soil.  In  this  way,  both  nitrogen  and  the  ash  constituents  are 
conserved  as  the  organic  matter  decays. 

Individual  characteristics  of  crops  may  be  taken  up  now  more 
in  detail. 

Wheat.  This  important  grain  represented  25  per  cent  of  the 
value  of  cereal  crops  and  13  per  cent  of  all  crops  in  1900.  Sixty- 
two  per  cent  of  the  cereal  products  milled  in  that  year  were  from 
wheat.  Over  one-third  of  the  farms  in  the  United  States  raised 
wheat,  with  a  total  production  in  1900  of  35  billion  bushels. 
Extensive  breeding  of  this  grain  has  led  to  the  production  of 
about  245  leading  varieties. 

The  crop  is  commonly  sown  in  the  fall  and  grown  as  "winter 
wheat."  As  a  result,  it  lias  a  longer  period  of  growth  and  a 
more  extensive  root  system  than  most  of  the  cereals.  The  roots, 
which  are  especially  developed  in  Durum  wheat,  have  been  found 
to  reach  a  length  of  four,  and  even  of  six  feet.  These  conditions 
enable  the  plant  to  feed  effectively  upon  the  soil.  The  necessary 
omission  of  spring  tillage  in  the  case  of  this  crop,  prevents  the 


190  Agricultural  Chemistry 

aid  of  this  important  stimulus  to  nitrification  and  renders  wheat 
dependent  largely  upon  manurial  supplies  of  available  nitrogen. 
Its  extensive  root  system  and  long  period  of  growth  aid  this  plant 
in  deriving  its  mineral  constituents  from  the  soil  and  make  it 
more  independent  of  available  potash  or  phosphate  fertilization ; 
nitrates  or  ammonium  salts  consequently  are  recommended  as  the 
chief  fertilizer  treatment. 

The  wheat  kernel,  according  to  Bessey,  is  separated,  mechan- 
ically into  the  following  proportion  of  parts : — 

Coatings  (or  bran  layers) 5          per  cent 

Gluten  layer 3 —  4        " 

Starch   cells    84—86 

Germ  6 

Protein  and  fat  are  highest  in  the  germ  and  bran,  ash  is  high- 
est in  the  bran,  and  the  fibre  is  confined  almost  exclusively  to 
this  coating.  Starch  is  the  characteristic,  and  by  far  the  most 
abundant  constituent  in  wheat,  as  it  is  in  all  the  cereal  grains. 
This  constituent  is  highest  in  the  flour,  which  represents  the  in- 
terior of  the  kernel.  (The  composition  of  grains  and  other  crops 
and  of  their  more  important  products  will  be  found  in  the  fourth 
table  in  the  Appendix.) 

It  is  a  significant  fact  that  about  80  per  cent  of  the  phosphoric 
acid  of  this  grain  is  located  in  the  bran.  This  makes  possible 
the  return  of  much  of  this  important  constituent  to  the  farm  in 
wheat  bran  and  its  eventual  recovery  in  the  manure.  The  gluten 
or  gum-forming  portion  of  the  wheat  grain  is  composed  of  two 
proteins,  glutenin  and  gliadin,  which  form  about  85  per  cent  of 
the  total  proteins  of  the  seed.  The  tenacity  of  bread  dough  and 
of  macaroni  made  from  wheat  flour,  is  due  to  gliadin.  Consid- 
erable attention  has  been  given  to  the  factors  affecting  the 
amount  and  composition  of  gluten  in  wheat  and  to  the  conse- 
quent milling  qualities  of  the  grain  and  baking  qualities  of  the 
flour.  According  to  Snyder,  the  most  valuable  wheats  for  bread 
making  purposes  are  those  in  which  80  to  85  per  cent  of  the 


Crops  191 

protein  is  gluten  and  the  gluten  is  composed  of  from  60  to  65 
per  cent  of  gliadin  and  35  to  40  per  cent  glutenin. 

Wheat  straw  has  little  value  to  the  stock  feeder  except  as  lit- 
ter. Experiments  have  shown  that  when  consumed  it  leaves 
little  surplus  of  food  value  to  the  animal  above  the  energy  re- 
quired for  mastication  and  digestion.  But  when  the  straw  is 
pulped  by  the  process  commonly  used  in  paper  making,  the  res- 
idual tissue  has  been  shown  to  have  a  food  value  equal  to  that  of 
starch.  The  plant  food  in  the  straw  should  be  saved  by  utiliz- 
ing it  as  litter  or  composting  in  the  manner  already  described. 

Rye,  like  wheat,  is  sown  chiefly  in  the  fall.  It  closely  re- 
sembles the  latter  in  its  composition  and  habits  of  growth.  The 
growth  of  this  crop  in  early  spring,  especially  wrhen  nitrification 
is  depressed  by  a  cold  wet  season,  may  be  stimulated  by  adding 
100  to  150  pounds  of  nitrate  of  soda  per  acre. 

Eye  grain  is  slightly  lower  in  fat  and  protein  than  is  wheat. 
Its  gluten  is  not  so  well  suited  for  bread  making  as  that  of  wheat, 
but  rye  flour  produces  a  coarse  bread  which  is  consumed  to  a 
considerable  extent.  The  straw  of  this  crop  is  high  in  fibre  and 
the  nutrient  compounds  which  it  contains  are  less  digestible  than 
those  of  oat  or  barley  straws,  so  that  it  possesses  little  feeding 
value. 

Barley  has  been  developed  into  many  varieties,  which  fall 
mostly  into  either  the  two  rowed  or  the  six  rowed  type.  It  may 
be  sown  in  the  fall  and  wintered,  but  it  is  more  distinctly  a 
spring  crop  than  is  rye  or  wheat.  It  is  hardier  than  the  latter, 
being  adapted  to  wider  ranges  of  latitude  and  climate.  The 
crop  grows  rapidly  and  is  more  exhaustive  of  surface  soil  min- 
erals than  the  cereals  already  discussed,  because  of  the  limited 
feeding  area  of  its  root  system.  This  limitation,  together  with 
its  comparatively  short  period  of  growth,  makes  the  crop  more 
dependent  upon  liberal  manuring  than  are  wheat  or  rye.  Spring 
tillage,  however,  aids  nitrification  and  reduces  the  requirement 
for  available  nitrogenous  manures.  Its  comparatively  limited 
root  system  and  short  time  of  growth  makes  it  especially  respon- 


192  Agricultural  Chemistry 

sive  to  soluble  phosphate  manuring.  Excessive  supplying  of  ni- 
trogen to  this  crop  is  to  be  avoided,  because  of  the  coarse  rank 
growth  which  it  induces  at  the  expense  of  seed  production. 

Barley  is  richer  than  wheat  in  ash,  fibre  and  protein ;  the  former 
two  constituents  are  largely  contributed  by  the  hull  of  this  grain. 
It  is  slightly  poorer  in  fat  and  carbohydrates  than  is  wheat. 
Barley  gluten  does  not  possess  the  property  required  for  bread 
making,  and  consequently  the  grain  finds  only  a  limited  use  for 
human  food.  It  is  fed  to  horses  and  cattle  and  is  highly  esteemed 
for  the  production  of  pork. 

The  production  of  malt  from  barley  gives  this  grain  its  chief 
value.  To  produce  this,  the  grain  is  soaked  in  water  for  some 
time  and  spread  upon  floors  in  thick  layers.  Germination  en- 
sues and  heat  is  evolved  in  the  process.  When  the  sprouts  are 
about  one-half  inch  long,  the  grain  is  heated  sufficiently  in  an 
oven  to  kill  the  embryo.  The  sprouts  are  then  removed,  dried 
and  ground,  and  put  upon  the  market  as  a  feeding-stuff  under 
the  name  of  malt  sprouts.  The  remaining  grain,  known  as 
"malt,"  does  not  differ  much  in  composition  from  the  original 
barley;  but  the  germinating  process  has  produced  and  activated 
an  enzyme  of  the  seed,  known  as  diastase.  If  the  malt  is  heated 
now  with  water  for  some  time  at  120°  F.,  a  process  known  as 
"mashing,"  this  enzyme  converts  the  starch  of  the  grain  into 
soluble  carbohydrates.  Diastase  has  been  found  capable  of  thus 
transforming  2000  times  its  own  weight  of  starch  into  dextrines 
or  maltose.  Since  the  amount  of  this  enzyme  in  barley  is  capable 
of  transforming  much  more  starch  than  is  associated  with  it, 
unmalted  barley  or  other  starchy  grains,  such  as  corn,  are  fre- 
quently added  to  the  mash.  The  maltose  produced  in  this  man- 
ner, together  with  other  substances,  is  dissolved  in  the  liquor  of 
the  mash  and  may  be  drawn  off  and  seeded  with  the  proper  yeast 
to  undergo  alcoholic  fermentation.  This  fermentation  results  in 
the  production  of  beer  and  other  liquors. 

The  residual  grain,  which  contains  the  fat  and  protein  orig- 
inally present,  is  placed  upon  the  feeding  stuff  market  as  wet 


Crops 

or  dried  brewers  grains.     The  latter  form  is  preferred  for  its 
more  economical  handling  and  better  keeping  qualities. 

Barley  straw,  when  used  in  feeding  experiments,  has  been 
shown  to  be  more  completely  digested  by  ruminants  than  is  the 
straw  of  wheat  or  rye,  thus  giving  it  a  limited  value  for  feeding 
purposes.  This  fact  has  also  been  demonstrated  by  practice. 

Oats  is  also  a  crop  which  spring  sowing  and  tillage  aids.  The 
spring  tillage,' in  preparing  the  land  for  sowing,  acts  as  an  aid  to 
nitrification  and  makes  it  unnecessary  to  apply  the  directly  avail- 
able nitrogenous  fertilizers.  But  its  short  growing  season  ren- 
ders it  dependent  upon  liberal  manuring  to  produce  maximum 
yields.  Excess  of  nitrogenous  manure  should  be  avoided  because 
of  the  disastrous  results  from  over-development  of  the  foliage  of 
the  crop  and  retardation  of  maturity.  Much  of  the  "lodging" 
of  oat  crops  on  heavy  soils  is  probably  due  to  excessive  produc- 
tion of  nitrates  from  humus  or  manure,  which  induces  a  rank 
growth  of  weak-stemmed  plants. 

Oat  grain  consists  of  approximately  70  per  cent  kernel  and 
30  per  cent  hull.  The  large  proportion  of  hulls  accounts  for  the 
high  fiber  and  ash  content  of  the  grain  and  reduces  its  digest- 
ibility. On  the  other  hand  it  appears  to  be  of  value  for  its  me- 
chanical, laxative  effect  upon  the  digestive  tract.  This  grain  is 
notable  among  the  cereals  on  account  of  its  high  content  of  fat. 
The  ground,  hulled  kernels,  known  as  "oatmeal,"  is  much  used 
for  "breakfast  foods."  The  residual  grain  and  poorer  kernels 
are  worked  into  oat  feeds.  Whole  oats  is  much  prized  by  the 
horse  feeder.  It  has  been  supposed  that  the  grain  possesses  pe- 
culiar tonic  properties,  due  to  a  specific  compound,  but  there  are 
no  scientific  data  in  support  of  this  view. 

Oat  straw  is  more  palatable  than  the  other  cereal  straws  and 
possesses  some  value  as  a  food  for  cattle  and  sheep. 

Corn,  or  maize,  has  formed  over  50  per  cent  of  the  acreage  of 
cereals  in  the  United  States  for  several  decades.  In  1900  it 
formed  56  per  cent  of  the  value  of  cereals  and  28.5  per  cent  of 
the  value  of  all  crops.  The  white  man  discovered  it  under  cul- 


194  Agricultural  Chemistry 

tivation  by  the  American  Indian  and  gave  to  it  the  name  Indian 
corn.  Continuous  breeding  has  developed  many  improved  va- 
rieties, which  differ  widely  in  size,  form,  color  and  chemical  com- 
position. The  common  varieties  of  corn  fall  under  three  sub- 
species: dent,  flint  and  sweet  corn.  By  far  the  greatest  number 
of  varieties  are  of  the  dent  species.  This  species  derives  its  name 
from  the  characteristic  indentation  of  its  crown,  due  to  shrinkage  . 
<?/  the  starch  cap  as  the  grain  dries.  Flint  corn  is  characterized 
by  a  smooth,  firm  coat,  supported  by  a  layer  of  hard  or  horny 
starch,  so  that  the  grain  retains  its  shape  as  it  dries.  Sweet  corn 
is  characterized  by  a  high  percentage  of  sucrose  and  develops  a 
prominently  wrinkled  surface,  as  a  result  of  shrinkage  in  drying. 

Examination  of  a  longitudinal  section  of  a  corn  grain  made 
by  splitting  it  across  the  thin  dimension,  shows  it  to  consist  of 
four  prominent  parts,  as  follows: — germ,  light  colored  starch 
cells,  dark  gluten  layers  and  a  thin  outer  coating.  The  germ  is 
located  at  the  tip  of  the  kernel  and  is  more  or  less  completely 
surrounded  by  starch,  which  forms  the  floury  portion  of  the 
grain.  Outside  the  starch,  nearly  or  completely  surrounding  it 
and  more  or  less  blending  with  it,  is  the  yellowish  gluten  layer. 
The  whole  kernel  is  covered  by  a  thin  coating  which  forms  a  small 
amount  of  bran  in  the  milling  process.  The,  germ  contains  most 
of  the  fat  of  the  corn  grain,  while  the  gluten  is  the  portion  richest 
in  protein.  That  portion  of  the  starch  bordering  upon  the  gluten 
layer  differs  in  character  from  the  common,  floury  starch,  and  is 
known  as  ' '  horny  "  or  "  glossy ' '  starch.  Almost  all  of  the  starch 
of  popcorn  is  of  this  variety. 

Corn  is  slightly  lower  in  protein  and  much  higher  in  fat  than 
is  wheat.  The  latter  constituent  is  sometimes  separated  from  the 
grain  on  a  commercial  scale  as  corn-oil.  Corn  meal  is  low  in 
fiber  and  pentosans,  the  carbohydrates  being  nearly  limited  to 
starch.  As  a  result,  corn  is  used  extensively  in  the  production 
of  sugar  by  the  process  already  described  under  1 1  glucose, ' '  the 
commercial  product  being  known  as  "corn  syrup."  The  residue 
from  this  process  is  sold  for  stock  feeding  as  gluten  feed.  To 


Crops  195 

a  limited  extent,  it  is  also  separated  into  such  fancy  feeds  as 
corn  bran,  gluten  meal  and  germ  oil  meal. 

The  corn  grain  is  low  in  ash,  containing  but  1.5  per  cent,  and 
extremely  deficient  in  lime;  this  constituent  forms  only  about 
2.3  per  cent  of  the  ash,  or  0.03  per  cent  of  the  grain.  It  is  thus 
apparent  that  corn  alone  forms  an  incomplete  ration  for  grow- 
ing animals  using  grain  alone,  such  as  swine. 

Corn  is  a  shallow  rooted  crop  and  requires  liberal  manuring. 
It  has  the  advantage,  however,  of  a  late  summer  growth,  so  that 
it  has  the  opportunity  of  assimilating  the  nitrates  produced  dur- 
ing the  hot  season.     Fresh  farm  manure  should  be  applied  to 
corn,  as  to  most  of  the  cereals,  at  the  rate  of  8  to  10  tons  per  acre. 
Rice  has  been  estimated  to  be  the  chief  food  of  over  one-half 
of  the  human  race.     It  differs  from  the  other  grain  crops  in  re- 
quiring a  warm  climate  and  abundance  of  water,  hence  it  is 
usually  grown  under  irrigation.     "When  so  grown  it  yields  two 
crops  and  requires  liberal  manuring.     Since  nitrification  is  sup- 
pressed on  rice  land,  nitrates  are  very  effective  with  this  crop. 
Composted  manures  are  used  for  the  crop  in  China  and  Japan. 
Rice  grain  is  extremely  low  in  ash,  fiber  and  fat,  and  contains 
but  about  7.4  per  cent  of  protein.     It  is  essentially  a  carbohy- 
drate food,  nearly  80  per  cent  of  it  being  starch.     The  rice  of 
commerce  is  a  product  of  a  milling  process  which  removes  the 
outer  husk  from  the  grain  and  yields  as  by-products,  rice  polish 
and  rice  bran.     The  former  is  fine  and  floury  and  much  richer 
than  the  grain  in  ash,  protein  and  fat,  while  the  latter  is  a  coarse 
material  high  in  percentages  of  ash  and  fiber.     The  two  by- 
products are  usually  mixed  and  sold  as  rice-meal,  or  rice-feed. 
Like  wheat,  and  in  contrast  to  most  of  the  other  grains,  rice  car- 
ries a  large  share  of  its  phosphorus  compounds  in  the  outer 
coatings,  which  makes  possible  a  considerable  recovery  of  phos- 
phoric acid  with  the  manure  produced  from  rice  feeds. 

Leguminous  seeds  differ  chiefly  from  the  seeds  of  cereals  by 
a  higher  content  of  protein  and  a  correspondingly  lower  content 
of  carbohydrates.  This  does  not  involve,  as  already  pointed  out, 


196  Agricultural  Chemistry 

a  heavy  demand  upon  the  soil  supplies  of  nitrogen.  Protein 
formation  in  these  crops,  however,  places  a  considerable  tax  upon 
the  ash  constituents  of  the  soil.  In  some  cases  the  carbohydrate 
material  of  these  grains  has  been  found  to  consist  chiefly  of 
galactans,  a  class  of  compounds  already  discussed  under  the 
' '  poly-saccharides ' '  of  the  plant.  Liberal  supplies  of  phosphoric 
acid,  lime  and  potash  are  required  for  these  crops.  A  number  of 
legumes  produce  seeds  which  form  a  considerable  bulk  of  the  total 
crop.  This  is  true  of  the  soy-bean,  horse-bean  and  cowpea.  The 
several  varieties  of  the  true  bean  and  the  pea  are  the  only  seeds, 
however,  of  much  commercial  importance.  The  soy-bean  and 
peanut  seeds  are  distinguished  by  high  percentages  of  fat, 
amounting  to  about  17  and  45  per  cent  in  the  grains,  respectively. 

Beans  thrive  best  on  light  clayey  soils,  well  stocked  with  lime, 
potash  and  phosphoric  acid.  Several  varieties  are  consumed, 
green  or  mature,  as  vegetables  and  are  valued  for  their  high 
protein  content.  The  soy-bean  was  introduced  from  Japan  and 
soy-bean  meal  finds  some  use  as  an  animal  feeding-stuff.  It 
resembles  the  bean  in  its  habits  of  growth. 

Peas  require  much  lime,  and  on  rich  soils  they  tend  to  produce 
luxuriant  vines  at  the  expense  of  seed.  The  fresh  seed  is  prized 
as  a  vegetable  and  cured  peas  are  valuable  for  pig  feeding.  It 
may  be  said  that  the  leguminous  crops  in  general  thrive  on  soils 
poor  in  nitrogen  but  well  supplied  with  the  other  elements  of 
fertility. 

Cotton-seed  is  one  of  several  miscellaneous  seeds  of  agricul- 
tural value.  The  seed  is  enveloped  by  the  lint  of  the  pod,  or 
"boll,"  of  the  plant.  American  cotton  yields  about  300  pounds 
of  lint  and  600  pounds  of  seed  per  acre.  The  seed  is  rich  in 
phosphoric  acid,  nitrogen  and  potash  and  the  crop  requires  ma- 
nurial  applications  of  these  constituents  in  the  order  given.  Cot- 
ton-seed oil  is  extracted  from  the  seed  by  pressure  and  also  by 
the  use  of  naphtha  as  a  solvent.  The  outer  coating,  or  hull,  of 
the  seed  is  generally  removed  previous  to  pressing,  in  which 
case  the  residue  is  known  as  decorticated  cotton  cake,  or,  when 


Crops  197 

ground,  as  cotton-seed  meal.  A  high  proportion  of  hulls  pro- 
duces a  dark  colored  meal  and  lowers  its  digestibility  and  food 
value.  The  meal  is  somewhat  valued  for  feeding  because  of  its 
high  protein  content,  but  because  it  contains  some  toxic  sub- 
stance, its  use  is  necessarily  restricted.  It  is  also  used  as  a  fer- 
tilizer, supplying  nitrogen  in  a  form  gradually  available  to  the 
crop.  Incidentally,  it  supplies  considerable  amounts  of  potash 
and  phosphoric  acid. 

Flax  seed,  or  linseed,  thrives  under  much  the  same  environ- 
ment as  that  required  by  wheat.  Where  grown  for  fiber,  the 
crop  requires  a  moist,  temperate  climate,  such  as  is  found  in  Ire- 
land, the  northern  United  States  and  Canada ;  but  seed  produc- 
tion requires  warmer  climates.  The  crop  produces  an  average 
yield  of  about  850  pounds  of  seed  and  2000  pounds  of  straw. 
Flax  requires  considerable  amounts  of  phosphoric  acid,  potash 
and  lime,  with  sufficient  nitrogen  to  induce  vigorous  growth. 

Linseed  resembles  cotton-seed  in  composition,  but  contains 
about  one-half  as  much  fiber  and  about  10  per  cent  more  fat, 
having  30  to  40  per  cent  of  the  latter  ingredient.  The  oil  is 
obtained  as  from  cotton  seed,  the  ground  residue  from  the  crush- 
ing method  being  known  as  "old  process"  linseed  meal,  or  "oil 
meal, ' '  while  that  obtained  by  solvents  is  known  as  "new  proc- 
ess" meal.  "Old  process"  meal  carried  8  to  12  per  cent  of  fat, 
while  the  new  process  of  extraction  leaves  only  2  to  4  per  cent 
of  this  constituent.  The  oil  obtained  from  flax  seed  of  the  region 
about  the  Baltic  Sea  in  Europe  is  preferred  in  the  paint  industry 
because  of  its  great  absorbing  power  for  oxygen.  Linseed  meal 
is  a  valuable  high-protein  food  for  stock. 

Hempseed  is  obtained  from  a  crop  resembling  flax  in  its  utility 
both  for  fiber  and  seed.  It  grows  best  in  a  temperate  climate 
and  resembles  corn  in  its  requirements  of  the  soil.  Hemp  yields 
500  to  1500  pounds  of  fiber  and  the  same  range  of  seed  per  acre. 
The  seed  is  used  as  poultry  food  and  the  oil  obtained  from  it 
is  sometimes  used  to  adulterate  linseed  oil. 

Buckwheat  has  much  the  same  composition  as  wheat.     It  has 


198  Agricultural  Chemistry 

the  advantage  of  thriving  upon  comparatively  light,  poor  soils. 
It  finds  limited  use  in  animal  feeding  and  as  human  food. 

Rape  seed  is  sometimes  grown  for  the  production  of  rape  oil 
or  colza  oil.  It  yields  over  40  per  cent  of  this  fat.  The  residue 
of  the  feed  is  used  as  manure,  because  it  lacks  relish  as  a  cattle 
food.  Rape  belongs  to  the  same  plant  family  as  the  turnip  and 
closely  resembles  it  in  manurial  requirements. 

The  castor  bean  is  the  seed  of  a  plant  grown  in  some  local- 
ities as  a  crop,  in  others  for  ornamental  purposes,  while  in  some 
cases  it  is  looked  upon  as  a  weed.  In  the  temperate  zone  it  is  an 
annual,  but  in  the  tropics  it  is  a  perennial  tree  of  considerable 
size.  It  is  an  adaptable  plant  but  thrives  best  on  rich,  sandy 
soils.  The  seed  is  valued  for  oil,  which  it  contains  to  the  extent 
of  50  per  cent.  This  oil  finds  appplication  medicinally  and  as  a 
lubricant.  The  residue  of  the  seed  is  suitable  for  manure,  but 
cannot  be  used  for  feeding  because  of  its  poisonous  properties, 
due  to  a  powerfully  toxic  protein,  known  as  ricin. 

Sunflower  seed  is  produced  in  yields  of  about  50  bushels  per 
acre.  The  dry  seed  contains  20  per  cent  of  an  oil  sometimes  used 
as  a  substitute  for  olive  oil.  It  also  contains  30  per  cent  of  fiber 
and  16  per  cent  of  protein,  the  latter  giving  to  the  seed  and  its 
residue  some  value  as  poultry  and  cattle  feeds.  The  crop  pro- 
duces heavily  on  soils  high  in  fertility. 

Hays  or  fodder  crops  include  true  hays  which  are  cut  at  the 
blossoming  or  early  seeding  stage,  and  in  which  the  stems  so  pre- 
dominate in  bulk  as  to  make  them  practically  straw  crops.  They 
have,  in  fact,  the  same  general  composition  and  food  require- 
ments as  the  cereal  grains,  irrespective  of  seed  production.  Un- 
der this  class  also  fall  the  cereal  grains,  such  as  barley  or  oats, 
when  cut  while  succulent  for  soiling  purposes  or  hay  making,  and 
corn  and  other  crops  cut  for  silage.  These  differ  from  the  cereal 
straws  as  a  result  of  their  comparative  immaturity.  The  leg- 
uminous plants  in  this  role  differ  from  the  corresponding  legumes 
raised  for  seed  in  the  same  manner  as  indicated  for  cereal  plants. 
They  are  cut  at  an  immature  stage  of  growth  when  the  foliage 


Crops  199 

far  outweighs  the  seed  in  amount  and  importance.     The  true 
hays  of  importance  are  comparatively  few  in  number. 

Timothy  is  perhaps  most  commonly  grown,  alone  or  associated 
with  clover.  It  is  representative  of  the  true  grasses,  as  a  class, 
being  high  in  fiber,  comparatively  low  in  protein,  and  rich  in 
potash  and  silica.  It  is  shallow  rooted  and  dependent  upon  lib- 
eral manuring.  It  grows  best  on  peaty  soils  and  hence  is  fav- 
ored by  heavy  applications  of  farm  manure.  The  application 
yearly  per  acre  of  90  to  180  pounds  of  nitrate  of  soda,  300  to  600 
pounds  of  bone  meal  and  70  to  140  pounds  of  chloride  or  sulphate 
of  potash  has  been  recommended  as  a  fertilizer  treatment. 

Red  top,  Hungarian  grass,  Kentucky  blue  grass  or  June 
grass,  orchard  grass  and  similar  hay  crops  resemble  timothy  in 
their  feeding  habits  and  composition  and  require  similar  manur- 
ing in  proportion  to  their  yield. 

Meadow  hay  and  pasture  grass  are  usually  a  mixture  of 
plants,  the  predominant  members  of  which  are  among  the  grasses- 
already  described,  or  others  closely  related  to  them.  The  peaty 
nature  of  the  surface  soil  in  permanent  meadows  is  attributed  to- 
the  decay  of  the  shallow  seated  root  system.  This  condition  fav- 
ors nitrification,  which  tends  to  exhaust  the  lime  by  the  leaching 
of  nitrate  of  lime  from  the  soil.  Such  crops  are  therefore  gen- 
erally responsive  to  applications  of  lime,  which  may  either  be 
applied  as  limestone,  burned  lime,  or  in  combination  with  phos- 
phoric acid,  as  basic  slag.  Heavy  dressings  with  farm  manure- 
or  commercial  fertilizers  tend  to  drive  out  the  valuable  clovers 
and  other  leguminous  plants  and  replace  them  with  coarser 
growtlis.  This  is  partly  due  to  the  production  of  an  acid  soil, 
which  may  be  restored  to  normal  condition  by  applications  of 
wood  ashes  or  lime.  Yearly  applications  of  plant  food  should  be 
made  to  these  permanent  crops. 

Cereal  hays  are  made  by  cutting  the  crop  when  the  grain  is 
in  the  milk  stage  and  just  preceding  the  most  active  migration 
of  nitrogen  and  ash  constituents  to  this  part  of  the  plant.  The 
nutrient  compounds  are  then  distributed  generally  through  the 


200  Agricultural  Chemistry 

plant  and  their  digestibility  is  less  depressed  by  cellulose  com- 
pounds than  is  the  case  at  maturity.  The  maximum  production 
of  tissue,  especially  desirable  with  these  crops,  will  be  promoted 
by  liberal  applications  of  nitrogenous  manures. 

Barley,  oats,  millet,  sorghum  and  other  cereals,  which  produce 
the  more  nutritious  straws,  are  utilized  for  hays.  They  may  be 
made  to  produce  enormous  yields,  but  at  the  expense  of  much 
plant  food.  Under  such  conditions,  they  must  be  considered  as 
particularly  exhaustive  crops  requiring  heavy  manuring. 

The  leguminous  hays,  while  comparatively  independent  of 
manurial  supplies  of  nitrogen,  are  sometimes  benefited  in  early 
stages  of  growth  by  the  application  of  soluble  forms  of  nitrogen. 
This  produces  a  plant  of  increased  vigor  and  promotes  further 
assimilation  of  food.  These  crops  feed  heavily  upon  lime,  potash 
and  phosphoric  acid.  This  fact  is  to  be  attributed  largely  to 
their  extensive  root  systems,  drawing  from  a  wide  range  of  soil 
for  a  large  production  of  dry  matter.  As  a  consequence,  these 
crops  are  especially  benefited  by  the  inorganic  constituents  of 
manures. 

The  reappearance  of  clover  in  limed  meadows  is  a  commonly 
observed  indication  of  the  value  of  this  fertilizer.  Wood  ashes 
benefit  these  crops  chiefly  by  reason  of  their  content  of  lime  and 
potash.  The  following  fertilizer  ration  per  acre  has  been  rec- 
ommended for  clover  and  alfalfa:  40  pounds  of  nitrate  of  soda 
or  1  ton  of  farm  manure ;  500  pounds  of  bone  meal ;  150  pounds 
of  muriate  or  sulphate  of  potash,  or  1500  pounds  of  wood  ashes : 
1  to  3  tons  of  ground  lime-stone,  as  required. 

Ensilage  is  properly  a  hay  crop.  It  is  principally  prepared 
from  corn,  although  sorghum,  millet,  clover,  cowpeas  and  other 
succulent  crops  have  been  so  treated.  The  production  of  good 
silage  depends  upon  careful  exclusion  of  the  air.  Under  this 
condition  the  mass  undergoes  changes  involving  the  consumption 
of  oxygen  and  production  of  compounds  not  previously  existing 
in  the  fresh  material.  The  temperature  of  the  mass  rises  and 
reaches  its  maximum  in  two  or  three  days.  These  changes  were 


Crops  201 

once  thought  to  be  due  chiefly  to  organisms  producing  alcohol, 
C2H5OH,  lactic  acid,  CH3CH01I.COOH,  and  acetic  acid,  CH3. 
COOH,  and  other  products  of  fermentation.  Babcock  and  Rus- 
sell, as  a  result  of  their  studies  on  silage,  have  concluded  that 
bacteria  are  not  the  essential  cause  of  the  changes  within  the  silo, 
but  are  probably  deleterious  and  exert  their  influence  only  in  the 
production  of  objectionable  putrefactive  changes.  These  inves- 
tigators further  conclude  that  the  changes  in  the  silo  are  chiefly 
due  to  the  respiration  of  living  plant  cells.  This  process  either 
may  involve  the  oxygen  confined  in  the  air  spaces  of  the  ensiled 
material,  in  which  case  it  is  known  as  direct  respiration,  or  it 
may  utilize  only  the  oxygen  of  compounds  in  the  plant  tissue, 
this  process  being  known  as  intra-molecular  respiration.  Both 
forms  of  activity  cease  with  the  death  of  the  plant  cells.  Hence, 
the  more  mature  the  corn  when  ensiled,  the  sooner  these  changes 
and  the  losses  incident  to  them,  cease.  This  theory  is  in  harmony 
with  the  practical  experience  that  rather  mature  corn  produces 
superior  ensilage.  Maximum  yield  of  material  and  the  produc- 
tion of  good  silage  are  secured  by  selecting  the  corn  when  in  a 
glazed  state. 

Chemical  changes  in  the  silo  entail  a  loss  of  dry  matter,  the 
amount  of  which  is  dependent  upon  the  care  with  which  air  is 
excluded.  In  the  majority  of  cases  investigated  this  loss  has 
been  from  15  to  20  per  cent  of  the  dry  matter  of  the  fresh  crop 
and  in  some  cases  it  has  reached  40  per  cent.  King  states  that 
the  loss  need  not  exceed  4  to  8  per  cent  for  corn  and  10  to  18 
per  cent  for  clover.  In  64.7  tons  of  silage  packed  in  a  silo,  tightly 
lined  with  galvanized  iron,  he  found  an  average  loss  of  6.38  per 
cent.  The  loss  was  estimated  for  eight  separate  layers  in  the 
whole  silo  and  found  to  be  32.53  per  cent  for  the  top  layer,  23.38 
per  cent  for  the  next,  and  from  2.1  to  10.25  per  cent  for  the 
others.  The  greater  loss  for  the  more  exposed  layers  emphasizes 
the  importance  of  oxygen  in  effecting  a  loss  of  dry  matter,  and 
the  need  of  excluding  air  from  the  material  by  tightly  packing  it. 
In  properly  cured  silage  the  loss  of  dry  matter  falls  chiefly  upon 
sugars,  which  are  hyrolyzed  to  organic  acids  and  ultimately  oxi- 


202  Agricultural  Chemistry 

dized  to  carbon-dioxide  and  water.  A  part  of  the  protein  com- 
pounds is  also  altered,  with  the  production  of  amino  acids.  In 
some  cases  over  one-half  of  the  nitrogen  of  the  silage  is  present 
in  the  latter  form.  This  is  two  to  three  times  as  much  as  the 
original  fodder  contains. 

Since  the  sugars  and  proteins  are  compounds  of  high  food 
value,  the  importance  of  restricting  such  losses  in  the  silo  is  evi- 
dent. Jordan  estimates  that  a  saving  of  three-fourths  or  even, 
of  one-half  the  average  losses  from  100  tons  of  corn  as  silage, 
would  increase  the  farmers '  food  resources  by  an  amount  equiva- 
lent to  from  5  to  7^  tons  of  timothy  hay. 

Root  crops  are  generally  gross  feeders  and  quite  dependent 
for  their  food  supplies  upon  readily  available  materials. 

The  turnip  is  a  biennial  plant  which  stores  food  the  first  sea- 
son and  produces  seed  the  second  year.  The  several  varieties 
differ  chiefly  in  the  form  and  color  of  the  root.  The  common 
turnip  contains  about  8  per  cent  of  dry  matter,  which  is  largely 
starch.  The  rutabaga,  or  Swede  turnip,  contains  more  dry  mat- 
ter (about  13  per  cent)  and  about  10  per  cent  of  carbohydrates. 
The  lower  content  of  water  than  in  the  turnip  promotes  better 
keeping  qualities.  Turnips  require  an  abundance  of  nitrogenous 
fertilizer  and  sulphur.  Investigations  in  this  country  indicate 
that  the  turnip  family  is  less  dependent  upon  readily  available 
forms  of  phosphoric  acid  than  other  crops. 

The  beet  is  cultivated  in  several  varieties.  It  is  a  deeper 
feeder  than  the  turnip  by  virtue  of  its  longer  tap-root.  The 
common  red  beet  contains  about  the  same  proportion  of  dry  mat- 
ter and  nutrients  as  the  rutabaga.  Mangel-wurzels,  or  field  beets, 
are  somewhat  poorer  than  the  red  beet  in  dry  matter,  and  notice- 
ably so  in  nitrogen-free  extract.  The  mangel  produces  a  large 
root  containing  about  12  per  cent  of  dry  matter.  The  sugar  beet 
is  a  smaller  variety  of  the  mangel.  It  contains  more  dry  matter 
(13  to  19  per  cent)  than  the  other  roots,  most  of  which  is  sucrose, 
CjalLjoOn.  The  production  of  beet  sugar  in  Europe  alone  for 
1903-1904  was  estimated  at  about  six  million  tons,  or  nearly 


Crops  203 

twice  the  world's  production  of  cane  sugar.  These  root  crops 
do  best  on  deep,  loamy  soil,  in  rather  warm,  damp  seasons,  ex- 
cept that  the  mangel  and  sugar  beet  require  rather  dry  fall 
weather.  Mangels  are  probably  the  most  exhaustive  farm  crop 
and  require  heavier  manuring  than  the  other  roots,  12  to  14  tons 
of  manure  per  acre  being  a  common  application.  They  are  less, 
dependent  than  turnips  upon  phosphate  fertilizers,  but  respond 
generously  to  applications  of  nitrate  of  soda  (about  200  pounds 
per  acre).  This  crop  is  also  benefited  by  the  addition  of  com- 
mon salt.  The  production  of  large  roots  is  sometimes  objection- 
able because  they  contain  much  more  water  than  small  ones.  This 
is  true  with  the  sugar  beet,  where  a  high  production  of  sugar  is 
desired.  Heavy  manuring  is  therefore  avoided  and  the  crop 
is  thickly  sown.  The  following  manuring  per  acre  is  recom- 
mended for  sugar  beets :  3  tons  of  stable  manure,  300  pounds  of 
acid-phosphate,  140  pounds  of  sulphate  of  potash.  The  soil 
should  be  well  stocked  with  lime. 

The  potato  is  a  surface  feeder  and  must  be  liberally  manured 
to  secure  good  yields.  This  crop  contains  20  per  cent  of  dry- 
matter,  which  is  mostly  starch.  It  is  a  staple  human  food  and 
is  also  fed  to  stock.  In  Europe,  one  of  the  principal  uses  for 
the  potato  is  for  the  manufacture  of  alcohol.  Stable  manure 
appears  to  favor  growth  of  scab  and  should  be  applied  to  a  pre- 
ceding crop.  Chloride  of  potash  is  also  said  to  be  injurious  to 
this  crop.  The  fertilizer  recommended  per  acre  is:  225  pounds, 
of  sulphate  of  ammonia,  500  pounds  of  acid-phosphate  and  200 
pounds  of  sulphate  of  potash. 

Fruit  crops  present  peculiar  manurial  requirements,  especially 
with  relation  to  perennial  growths  in  which  the  stems  serve  as 
reservoirs  of  nutrient  elements.  The  composition  of  the  20  per 
cent  of  dry  matter  in  common  fruits  is  principally  of  carbo- 
hydrate nature  (invert  sugar,  sucrose,  cellulose,  pentosans  and 
pectose)  with  small  amounts  of  organic  acids,  ash  and  nitrogen 
compounds.  Green  fruit  contains -starch,  which  is  converted  to 
sugar  in  the  ripening  process.  The  production  of  these  com- 


204  Agricultural  Chemistry 

pounds  creates  special  demands  for  potash  and  phosphoric  acid. 
The  strawberry,  blackberry  and  similar  fruits  will  produce  the 
best  yields  when  a  vigorous  cane  growth  is  induced  by  liberal 
manuring.  They  thus  respond  most  markedly  to  applications 
of  liquid  manure.  The  fruit  of  trees  draws  its  nutrients  from 
an  extensive  woody  growth  and  volume  of  sap,  but  these  sources 
must  be  reinforced  to  keep  the  trees  in  vigorous  bearing  condi- 
tion. Light  yearly  applications  of  farm  manure  or  complete 
fertilizers  are  recommended  for  these  crops. 

Forest  growth  presents  practically  the  same  demands  on  fer- 
tility as  do  fruit  trees,  but  as  has  been  pointed  out,  this  demand 
is  practically  covered  by  a  continuous  return  of  plant  food  from 
this  crop  to  the  soil. 

The  miscellaneous  crops,  grown  chiefly  for  the  truck  market, 
give  cash  returns  which  justify  the  expense  of  forcing  rations 
of  plant  food.  Such  rations  should  include  liberal  amounts  of 
nitrogen.  Tobacco  should  receive  some  nitrogen  and  a  liberal 
supply  of  potash,  with  phosphoric  acid  in  moderate  amount.  Too 
much  nitrogen  is  to  be  avoided  because  of  unfavorable  effects  on 
the  quality  of  the  tobacco  leaf.  Cotton-seed  meal  at  the  rate  of 
200  to  300  pounds  per  acre  before  planting  is  a  favorable  ration. 
Potash  should  be  applied  as  sulphate  (100  Ibs.),  as  the  chloride 
is  injurious.  Phosphoric  acid  should  be  applied  at  the  rate  of 
200  pounds  of  acid-phosphate  or  400  pounds  of  bone  meal  per 
acre. 

Cabbages,  as  a  market  crop,  are  brought  to  harvest  early  and 
are  improved  in  quality  by  heavy  applications  of  nitrogen.  Ni- 
trate of  soda  or  sulphate  of  ammonia  at  the  rate  of  300  pounds 
per  acre  in  two  or  three  top  dressings  is  recommended  in  addi- 
tion to  general  manuring. 

No  specific  rules  can  be  laid  down  for  the  application  of  fer- 
tilizers to  each  crop,  because  of  the  greatly  variant  conditions  of 
soil  and  climate  under  which,  it  must  be  grown.  These  factors, 
particularly  the  latter,  exert  a  profound  influence  on  the  growth 
of  plants.  Each  farmer  must  determine  the  requirements  of  his 


Crops 


205 


own  conditions  by  the  fertilizer  tests  described  in  the  chapter 
on  "Fertilizers." 

Factors  influencing  the  composition  of  the  crop  are:  Stage 
of  growth,  exposure  at  harvest,  fertilizers  and  environment. 

The  stage  of  growth  has  been  shown  to  present  marked  differ- 
ences in  the  feeding  value  of  the  straw  of  cereal  plants.  In  the 
true  hay  crops  the  grain  takes  up  most  of  the  nutrients  of  the 
plant  during  the  ripening  period.  This  results  in  increased  fiber 
content  and  decreased  feeding  value  of  the  stems.  The  Connec- 
ticut Experiment  Station  gives  the  following  composition  of 
timothy  at  successive  periods  preceding  ripening. 

Composition  of  Dry  Matter  of  Timothy 


Stage  of  growth 

Ash 

Crude 
protein 

Crude 
fiber 

Nitrogen 
free 
extract 

Ether 
extract 

Well  headed  out.  .  .  . 
In  full  bloom  

Per  cent 
4.7 
4.3 

Per  ceni 
9.6 
7.1 

Per  cent 
33.0 
33.3 

Per  cent 
50.8 
53.3 

Per  cent 
1.9 
2.0 

When  out  of  blossom 
Nearly  ripe  

4.1 
3.6 

7.1 
6.8 

33.8 
35.4 

53.3 
52.2 

1.7 

2.0 

It  will  be  observed  that  the  protein  and  ash  of  the  hay  decrease 
rapidly  from  the  heading  out  stage,  while  the  fiber  increases  at 
the  later  stages.  The  nitrogen-free  extract  at  the  later  stages  is 
probably  less  valuable  than  at  the  earlier  periods  of  growth  as 
a  result  of  increased  proportions  of  indigestible  pentosans  and 
similar  compounds.  Thus,  while  the  hay  crops  increase  in  the 
quantity  of  dry  matter  to  the  end  of  the  ripening  period,  they 
decrease  in  palatability  and  food  value  when  harvesting  is  de- 
layed too  long.  These  conditions  are  more  serious  with  legume 
hays,  where  a  large  percentage  of  protein  is  involved.  This  is 
shown  in  the  following  table  on  the  composition  of  alfalfa  hay 
published  by  the  Kansas  Experiment  Station. 


206 


Agricultural  Chemistry 


The  decrease  in  protein  at  the  last  stage  is  marked.  These 
data  indicate  that  the  most  favorable  mean  between  quantity  and 
quality  of  crop  will  be  secured  by  cutting  grasses  and  clovers 
between  early  and  full  bloom. 

Composition  of  Dry  Matter  of  Alfalfa  Hay 


Ash 

Crude 
protein 

Crude 
fiber 

Nitrogen 
free 
extract 

Ether 
extract 

First  stage   (about   10 
per  cent  in  bloom) 
Second  stage  (about 
50  per  cent  in  bloom) 
Third      stage        (full 
bloom  )  

Per  cent 
10.45 
10.28 
8.45 

Per  cent 
18.50 
17.21 
14.43 

Per  cent 
32.20 
35.37 
36.10 

Per  cent 
27.29 
34.00 
39.62 

Per  cent 
1.56 
1.05 
1.41 

With  corn,  conditions  are  different.     Analyses  at  the  Maine 
Experiment  Station  gave  the  following  data: 

Composition  of  Dry  Matter  of  Corn  Plant 


Stage  of  growth 

Ash 

Crude 
protein 

Crude 
fiber 

Sugar 

Starch 

Nitro- 
gen 
free 
extract 

Ether 
extract 

Very  immature 
(Aug.  15)  

Per 

cent 

9.3 
6.5 
6.2 
5.6 
5.9 

Per  cent 
15.0 
11.7 
11.4 
9.6 
9.2 

Per 

cent 

26.5 
23:3 
19.7 
19.3 
18.6 

Per 
cent 

11.7 
20.4 
20.6 
21.1 
16.5 

Per  cent 

Per  cent 
46.6 
55.6 
59.7 
62.5 
63.3 

Per  cent 
2.6 
2.9 
3.0 
3.0 
3.0 

A  few  roasting  ears 
(Aug.  28)  

2.1 

4.9 
5.3 
15.4 

All  roasting  stage 
(Sept.  4)  .  , 

Some  ears  glazing 
(Sept.  12)  

All  ears  glazed 
(Sept,  21)  .. 

Crops 


207 


The  material  increase  in  starch  and  other  digestible  carbo- 
hydrates more  than  offsets  the  relative  decrease  in  crude  protein 
and  is  accompanied  moreover  by  a  decrease  of  crude  fiber.  Feed- 
ing experiments  moreover  have  shown  that  mature  corn  is  more 
digestible  than  the  immature  plant,  both  as  fodder  and  as  silage. 

Exposure  to  the  weather,  particularly  undue  exposure  to 
rainy  weather,  detracts  from  the  value  of  the  crop.  This  is  due 
to  the  leaching  away  of  nutrient  compounds  by  the  rain. 

The  following  table  from  Bulletin  135  of  the  Kansas  Station 
shows  the  extent  of  such  losses  from  alfalfa  hay,  assuming,  as  is 
approximately  true,  that  no  fiber  is  lost.  The  hay  was  exposed 
for  15  days,  during  which  time  it  was  subjected  to  three  rains 
amounting  to  1.76  inches: — 

Losses  by  Rain  to  100  Pounds  of  Alfalfa  Hay 


Crude 
Ash 

Crude 
protein 

Crude 
fiber 

Kitro- 
gen 
free 
extract 

Crude 
tat 

Total 

Pounds  in  original  

12.2 

18.7 

26.5 

38.7 

3.9 

100.0 

Pounds  in  damaged  

8.7 

7.5 

26.5 

23.0 

2.6 

68.3 

Pounds  lost  

3.5 

11.2 

00.0 

15.7 

1.3 

31.7 

Per  cent  lost  

28.7 

60.0 

00.0 

41.0 

33.3 

31.7 

Not  only  has  nearly  one-third  of  the  total  dry  matter  been  lost, 
but  over  one-third  of  this  loss  has  fallen  upon  protein,  which  is 
the  most  valuable  constituent  of  the  hay.  For  every  pound  of 
protein  in  the  damaged  hay,  one  and  one-half  pounds  have  been 
lost  by  exposure. 

Curing  processes  may  seriously  affect  the  composition  of 
crops.  Alfalfa  hay  furnishes  a  striking  example  of  this  fact. 
When  cut  early,  this  crop  bears  73  pounds  of  leaf  for  100  pounds 
of  stem.  The  leaf,  however,  is  much  richer  in  nutrients  than 
the  stem.  Thus,  for  100  pounds  of  each  constituent  in  the  stems, 


208  Agricultural  Chemistry 

the  leaves  of  an  equivalent  amount  of  crop  in  each  case  will 
contain  of:  fat,  450  pounds;  protein,  250  pounds;  nitrogen  free 
extract,  135  pounds;  crude  fiber,  28  pounds.  That  portion  of 
the  crop  especially  subject  to  mechanical  loss  in  hay  making  is 
therefore  the  most  valuable  as  fodder. 

Headden  has  estimated  the  mechanical  loss  of  alfalfa  in  har- 
vesting at  15  to  20  per  cent  of  the  dry  crop.  In  extreme  cases  60 
per  cent  or  more  may  be  left  on  the  field.  This  loss  falls  chiefly 
upon  the  leafy  tissue.  More  valuable  hay  will  be  secured  if  the 
crop  is  cut  between  early  and  full  bloom  and  handled  to  a  mini- 
mum extent,  than  if  it  is  allowed  to  become  brittle  by  aging  or 
over-curing  at  harvest  and  then  excessively  handled. 

Fertilizers  influence  the  composition  of  the  crop  to  a  limited 
extent,  both  by  their  amount  and  their  nature.  This  effect  has 
been  observed  principally  with  reference  to  the  increase  of  pro- 
tein formation  by  application  of  nitrogenous  fertilizers.  Pingree 
found  that  nitrogen  applied  to  oats,  in  the  form  of  dried  blood, 
slightly  increased  the  protein  content  of  both  grain  and  straw. 
At  the  Storrs  (Conn.)  Experiment  Station,  corn,  oats  and  mixed 
grass  (timothy,  red  top  and  Kentucky  blue  grass)  were  supplied 
with  gradually  increasing  amounts  of  nitrogen,  added  to  a  uni- 
form ration  of  potash  and  phosphoric  acid.  Within  certain 
limits,  the  protein  content  of  the  corn  and  oat  grains,  oat  straw, 
corn  stover  and  grasses  was  increased,  somewhat  in  proportion 
to  the  amounts  of  nitrogen  supplied.  Parozzani  found  that  in- 
creased application  of  super-phosphates  to  corn  resulted  in  a 
corresponding  increase  of  total  phosphoric  acid  in  the  seed.  In- 
vestigation of  the  distribution  of  phosphorus  in  the  seed  showed 
that,  while  the  amount  in  nuclein  compounds  remained  constant, 
the  amounts  in  the  forms  of  lecithin  and  phytin  were  increased. 
Total  nitrogen  in  the  seed  was  not  sensibly  affected,  but  the  pro- 
portion of  true  protein  compounds  was  slightly  increased  and 
this  increase  was  limited  to  a  specific  protein,  namely,  zein. 

Such  examples  as  these  are  limited.  From  an  intimate  knowl- 
edge of  the  long  series  of  fertilizing  experiments  at  Rothamsted, 


Crops  209 

Hall  is  led  to  state  that,  "Although  the  composition  and  quality 
of  the  grain  is  affected  by  the  amount  of  nitrogen  supplied  to  the 
crop,  it  is  really  astonishing  to  find  how  small  are  the  changes 
brought  about  by  extreme  differences  in  manuring. ' '  The  effects 
may  be  more  marked  with  other  parts  of  the  crop,  but,  quoting 
Hall  further:  "The  crop  reacts  against  variations  in  the  com- 
position of  the  soil  and  tends  to  keep  its  own  composition  con- 
stant. "When  also  the  time  comes  for  the  grain  to  be  formed 
from  the  reserve  materials  already  stored  up  in  the  plant,  an- 
other attempt  is  made  to  turn  out  a  standard  product.  Even  on 
the  Rothamsted  plots,  where  the  differences  in  the  supply  of 
nutrients  are  extreme  and  have  been  accumulating  for  50  years, 
the  composition  of  the  grain  changes  more  from  one  season  to 
another  than  it  does  in  passing  from  plot  to  plot. ' ' 

Environment  has  been  found  to  influence  the  composition  of 
the  crop  more  than  any  other  factor.  The  sugar  beet  has  given 
valuable  results  along  this  line  in  experiments,  conducted  by 
Wiley  in  this  country  from  1900  to  1905.  Beets  were  grown 
from  the  same  seed  at  12  experiment  stations  scattered  from 
Kentucky  to  Wisconsin  and  from  New  York  to  California.  At 
Utah,  California  and  Colorado  the  crops  were  grown  under  ir- 
rigation. Chemical  and  meteorological  records  were  carefully 
kept  in  all  cases.  As  a  result  of  this  and  similar  investigations, 
Wiley  concludes  that  the  soil  and  fertilizers  have  only  a  limited 
influence  and  that  temperature  (or  latitude)  is  the  most  potent 
element  of  the  environment  in  the  production  of  a  beet  rich  in 
sugar.  Excessive  rain  fall  and  irrigation  affect  the  beet  only  in- 
cidentally by  increasing  the  yield  with  a  proportionate  reduction 
in  percentage  of  sugar,  and  dry  tillage  produces  opposite  effects. 
With  these  conclusions  as  a  basis,  there  has  been  mapped  for  the 
northern  United  States  a  belt  of  country  which  presents  optimun 
climatic  conditions  for  the  production  of  sugar  beets. 

Wheat  has  been  tested  in  a  similar  manner  and  the  results 
have  been  reported  recently  by  Le  Clerc.  Crops  were  growrn 
from  the  same  seed  at  the  apices  of  two  great  triangles ;  namely : 


210  Agricultural  Chemistry 

Kansas,  South  Dakota  and  California;  and  Kansas,  Texas  and 
California.  The  results  demonstrate  that  the  same  variety  of 
wheat  brought  from  different  localities  and  grown  side  by  side  in 
one  locality,  yields  crops  of  almost  the  same  appearance  and  com- 
position. On  the  other  hand,  "wheat  of  any  one  variety  from 
any  one  source  and  absolutely  alike  in  chemical  and  physical 
characteristics,  when  grown  in  different  localities,  possessing  dif- 
ferent climatic  conditions,  yields  crops  of  very  widely  different 
appearance  and  very  different  chemical  composition."  Thus, 
with  relation  to  protein,  the  constituent  of  most  concern,  the 
seed  of  Kubanka  wheat  grown  in  South  Dakota  in  1905  contained 
13.03  per  cent.  The  1906  crop  grown  from  this  seed  contained : 
in  Kansas,  19.85  per  cent  of  protein  in  the  seed,  in  California, 
9.68  per  cent,  and  in  South  Dakota,  14.24  per  cent.  The  seed 
from  these  localities  grown  in  1907  at  California  contained  9.70, 
9.90  and  9.05  per  cent  of  protein  in  the  seed,  respectively,  while 
portions  of  the  same  seeds  grown  in  South  Dakota  contained 
14.24,  13.89  and  12.87  per  cent  of  protein.  The  same  condition 
obtained  with  Crimean  wheat  grown  in  the  other  triangle,  Kan- 
sas uniformly  producing  the  highest  protein  content  in  the  grain 
and  California  the  lowest.  These  results  lead  to  the  conclusion 
that  a  crop  should  lie  improved  by  selection  in  the  region  where 
it  is  to  be  grown,  or  that  "seed  should  be  selected  from  a  region 
of  similar  climatic  condition." 

The  author  just  quoted  compared  eight  samples  of  Durum 
wheat  grown  in  arid  and  semi-arid  regions  with  seven  samples 
of  the  same  variety  from  humid  regions.  The  seed  from  dry 
regions  contained  17.23  per  cent  of  protein,  and  that  from  humid 
regions,  13.75  per  cent ;  and  the  samples  weighed  30.3  grams  and 
33.5  grams  per  1000  grains,  respectively.  Abundant  water  sup- 
ply is  thus  productive  of  plump,  starchy  grains,  while  dry  con- 
ditions produce  a  smaller  grain  richer  in  protein.  This  contrast 
is  illustrated  by  the  change  in  composition  of  Durum  wheat 
grown  in  Mexico.  The  original  seed  contained  12.3  per  cent  pro- 
tein. Grown  under  irrigation  it  produced  seed  of  11.1  per  cent 


Crops  211 

protein,  non-irrigated,  17.7  per  cent.  Shutt  has  confirmed  these 
data  with  wheat  grown  on  irrigated  and  non-irrigated  soil  at 
Manitoba,  Canada.  Lawes  and  Gilbert  had  previously  observed 
at  Rothamsted  that  hot,  moderately  dry  seasons  produced  the 
best  quality  of  wheat. 

Sweet  corn  has  been  similarly  tested  by  Wiley  for  several  suc- 
cessive years.  The  results  have  shown  that  the  content  of  sugar 
is  less  influenced  by  temperature  than  in  the  case  of  the  sugar 
beet.  The  ripening  crop  was  followed  along  the  Atlantic  coast 
from  Florida  to  Maine.  Contrary  to  the  results  with  the  sugar 
beet  the  higher  average  content  of  sugar  appeared  to  be  found 
in  the  warmer  climates.  The  lower  temperatures  of  the  North, 
however,  retard  the  ripening  process  and  render  the  corn  suc- 
culent for  a  longer  period  than  does  the  warm  climate  of  the 
extreme  South.  Wiley  concludes  that  the  amount  and  distribu- 
tion of  rainfall  is  the  most  important  factor  affecting  the  edible 
quality  of  green  sweet  corn,  and  that  the  favorable  effects  of 
moderate,  well  distributed  rain-fall  indicate  that  the  northern 
states  will  continue  to  produce  the  best  crop  outside  the  irrigated 
districts.  But  no  special  area  for  sweet-corn  growing  can  be 
mapped  as  has  been  done  in  the  case  of  the  sugar  beet. 

Crop  rotation  should  be  rationally  based  upon  the  varying  de- 
mands of  crops  for  plant  food  and  the  characteristic  feeding 
habits  of  individual  species  of  plants.  When  the  plant  food  of 
the  surface  soil  has  been  exhausted  by  such  shallow  rooted  crops 
as  corn,  grasses  and  turnips,  they  should  be  followed  by  deep 
rooted  crops,  such  as  wheat,  mangels,  or  alfalfa.  Not  only  will 
the  latter  crops  obtain  their  supplies  of  food  from  the  lower 
layers  of  the  soil,  but  they  leave  a  portion  of  it  at  the  surface 
in  foots  and  stubble,  from  which  it  becomes  available  to  succeed- 
ing crops.  No  more  striking  example  of  this  fact  is  furnished 
than  that  of  alfalfa.  According  to  Headden,  the  roots  and  stub- 
ble of  alfalfa  to  a  depth  of  G1/^  inches  contain  approximately 
2.86  tons  of  dry  matter  per  acre,  having  the  following  constit- 
uents :  total  ash  172  pounds ;  phosphoric  acid  24  pounds ;  sulphur 


212 


Agricultural  Chemistry 


trioxide  9  pounds;  lime  50.5  pounds;  chlorine  6.5  pounds;  mag- 
nesia 15.15  pounds;  potash  44.5  pounds;  and  104  pounds  of  ni- 
trogen. Reference  to  the  table  in  the  Appendix  which  gives 
"Plant  food  removed  by  crops,"  shows  that  the  stubble  of  al- 
falfa alone,  places  in  the  surface  soil  as  much  plant  food  as  is 
removed  by  total  cereal  crops. 


Note  the  difference  in  depth  of  the  root  systems  of  alfalfa  and  corn. 
The  scales  give  the  full  depth  in  feet. 


Crops  213 

The  waste  tops  of  the  mangel  crop  can  also  restore  to  the  soil 
as  much  food  as  is  required  by  an  average  grain  crop.  Not  only 
will  this  practice  bring  fertilizing  elements  from  deeper  layers 
of  the  soil  to  the  surface,  but  the  deeply  growing  root  systems 
of  such  crops,  and  the  deep  thorough  tillage  demanded  by  them, 
will  benefit  the  physical  condition  of  the  soil  when  they  are 
grown  in  rotations.  In  addition  a  rotation  effects  a  cleaning  of 
the  land  which  may  mean  both  the  partial  eradication  of  such 
parasites  as  fungi,  molds,  etc.,  and  in  addition  the  tolerance  of 
a  given  plant  for  the  decomposing  residues  of  its  predecessor, 
which  might  be  toxic  to  itself. 

Increase  of  soil  nitrogen  is  the  most  valuable  effect  produced 
by  legume  crops  grown  in  systems  of  rotation.  In  this  connec- 
tion the  work  of  Shutt  in  Saskatchewan,  Canada,  is  of  interest. 
He  compared  a  virgin  soil  of  that  province  with  one  that  had 
been  continuously  cultivated  to  cereal  grains  or  fallow  for  20 
years.  The  cultivated  soil  contained  0.253  per  cent  of  nitrogen 
(to  a  depth  of  8  inches)  and  the  virgin  soil  contained  0.371  per 
cent.  This  difference  represented  a  loss  of  2200  pounds  of  nitro- 
gen per  acre  by  the  system  of  cultivation  practiced.  Investi- 
gating the  possibility  of  restoring  nitrogen  to  the  soil,  Shutt  grew 
common  red  clover  upon  a  poor  sandy  soil,  cutting  the  crop  twice 
yearly  and  leaving  it  upon  the  soil.  At  the  end  of  each  second 
season  the  crop  was  turned  in  and  the  plot  re-sown  the  next 
spring.  In  five  years  of  this  treatment  the  soil  gained  over  300 
pounds  of  nitrogen  per  acre  to  a  depth-  of  four  inches,  despite 
inevitable  losses  by  nitrification  and  leaching. 

The  effect  of  the  growth  of  clover  on  succeeding  crops  was 
demonstrated  by  Shutt  in  field  experiments.  Two  series  of  plots 
were  used,  on  one  of  which  clover  was  compared  with  wheat, 
while  on  the  other  oats  and  clover  were  compared  with  oats. 
The  first  series  will  be  described.  On  one  plot,  clover  was  sown 
alone  and  one  cutting  made  and  removed.  The  crop  was  turned 
under  in  the  following  spring.  On  the  other  plot,  wheat  was 
grown  and  harvested  as  usual.  The  effect  of  this  treatment  was 


214 


Agricultural  Chemistry 


observed  on  grain  and  root  crops  for  three  succeeding  years,  with 
the  following  resultant  data: — 

Increase  of  Crop  Due  to  Growth  of  Clover 


1900 

1901 

1002 

1903 

Tuns 

Lbs. 

Bush. 

Lbs. 

Tons 

Lbs. 

Plot  A:  Clover  

Corn 

27 

1,  760 

Oats 

75 

10 

Sugar 
beets 

22 

600 

PlotB:  Wheat  

Coi  n 

19 

1,280 

Oats 

51 

26 

« 

8 

1  260 

Increase  due  to  clover 

Corn 

8 

480 

Oats 

23 

18 

« 

13 

1,340 

This  effect  was  obtained  without  a  sacrifice  of  the  crop  and 
must  have  been  chiefly  due  to  the  nitrogen  supplied  by  the  stub- 
ble and  second  growth  of  the  clover. 

The  distribution  of  nitrogen  in  the  legume  crop  bears  an  im- 
portant relation  to  its  proper  use  in  rotations.  Shutt  gives  the 
distribution  of  nitrogen  between  the  roots  and  stubble  and  the 
tops  of  legumes  as  follows: — 

Nitrogen  in  Legumes. 


Legumes:  One  season's  growth 

Nitrogen  in  parts  of  crop 
(Pounds  per  acre  of  crop) 

In  tops 

In  9  in.  depth  of 
root  and  stubble 

90 
82 
85 
75 
129 
82 
63 
119 

48 
48 
19 
61 
18 
13 
15 
10 

Clover,  crimson  

Alfalfa  

Horse  bean  

Pea  

Crops  215 

The  proportion  of  the  total  nitrogen  of  the  crop  contained  in 
the  roots  of  common  red  and  mammoth  clovers  and  alfalfa  indi- 
cate the*  effectiveness  of  the  residues  of  these  crops  as  sources  of 
nitrogen,  when  they  are  grown  in  rotations  and  the  crop  har- 
vested. The  figures  for  alfalfa  are  probably  much  below  the 
average  and  fail  to  do  justice  to  the  crop.  The  condition  is  dif- 
ferent with  shadow  rooted  legumes.  Thus,  with  the  vetch  and 
pea,  a  large  supply  of  nitrogen  in  the  tops  is  correlated  with  a 
comparatively  small  amount  in  the  roots.  Marked  benefit  from 
these  crops  in  rotations  can  be  secured  only  where  the  whole 
growth  is  turned  in.  Snyder  states  that  the  nitrogen  content  of 
the  soil  can  be  maintained  and  even  slightly  increased  when 
clover  is  grown  two  years  in  a  five  course  rotation  with  grains 
and  timothy  to  which  farm  manures  are  applied. 


CHAPTER  IX 


THE  ANIMAL  BODY 

The  elements  found  in  animal  tissue  are  the  same  as  those 
found  in  the  plant  world,  and  while  sodium  and  chlorine  are  con- 
sidered by  some  as  non-essential  for  plant  development,  in  the 
formation,  of  the  animal 's  tissue  they  are  indispensable.  Fluor- 
ine and  silicon  are  also  always  found  in  the  animal  body,  but  are 
not  known  to  be  absolutely  essential  for  life  or  growth.  Fluorine 
occurs  in  small  quantities  in  the  teeth  and  bones,  and  silicon  in 
the  hair,  wool  and  feathers. 

The  compounds  forming  the  animal  body  are  many  and  very 
complex  and  only  a  brief  survey  of  the  principal  ones  can  be 
given  here. 

The  constituents  of  the  animal  body  may  be  divided  into: — 

(1)  Inorganic  compounds,  including  water,  various  acids  and 
numerous  salts ;  some  are  in  the  solid  state,  as  the  calcium  phos- 
phate of  the  bone ;  others  are  in  solution  as  the  sodium  chloride 
of  the  blood. 

(2)  Organic  compounds, 


Simple-proteins, 
ammo-acids,  etc. 

Conjugated-proteins 

Derived 
proteins 

Albumins 

Nucleo-proteins 

Proteoses 

Globulins 
Albuminoids 
Amino-acids 
Amides 

Phospho-proteins 
Glyco-proteins 

Peptones 

(  b  )  Non  -n  i  tr  ogen  ous  .  . 

Fate 
Carbohydrates 

Of  the  inorganic  constituents,  by  far  the  largest  part  is  con- 
tained in  the  bones.  In  fat  animals  75  to  85  per  cent  of  the 
total  ash  constituents  of  the  body  are  found  in  the  bones.  Bone 


The  Animal  Body  217 

ash  consists  of  phosphate  of  calcium,  with  a  small  quantity  of 
carbonate  of  calcium  and  phosphate  of  magnesium.  In  muscle 
by  far  the  most  abundant  ash  constituent  is  phosphate  of  potas- 
sium. Potassium  salts  are  also  abundant  in  the  "yolk"  of  un- 
washed wool  and  in  the  sweat  of  horses  and  other  animals. 
Blood,  on  the  other  hand,  always  contains  a  preponderance  of 
sodium  salts. 

The  nitrogenous  substances  constituting  the  animal  body  are 
extremely  varied  in  character  and  properties  and  it  would  be 
impossible  in  a  book  of  this  kind  to  attempt  to  describe  them  in 
detail.  The  albumins  and  globulins  form  the  substance  of  ani- 
mal muscle  and  nerve,  and  the  greater  part  of  the  solid  matter 
of  blood.  They  are  undoubtedly  of  the  greatest  importance  in 
the  animal  economy.  The  albuminoids  form  the  substance  of 
skin  and  sinew,  of  all  connective  tissue,  and  also  the  protein  ma- 
terial of  cartilage  and  bone.  They  are  simple  proteins,  which 
possess  essentially  the  same  chemical  structure  as  the  other  pro- 
teins, but  are  characterized  by  great  insolubility  in  all  neutral 
solvents.  Keratin,  the  principal  protein  of  horn,  hair,  wool  and 
feathers,  belongs  to  this  class.  The  remarkable  difference  in  the 
properties  of  the  protein,  keratin,  and  the  protein,  serum-albu- 
min, lies  in  the  internal  structure  of  their  respective  molecules. 

The  nucleo-proteins  always  contain  phosphorus  and  are  con- 
tained in  every  cell.  They  are  of  special  importance  in  all  life 
processes.  The  phospho-proteins  are  represented  in  the  animal 
kingdom  by  the  important  nitrogenous  body  found  in  milk, 
namely,  casein.  This  class  of  bodies  is  also  represented  in  the 
yolk  of  the  egg,  in  the  form  of  the  protein,  vitellin.  These  phos- 
pho-proteins contain  phosphorus  just  as  the  nucleo-proteins  do, 
but  differ  in  their  internal  structure  from  those  bodies.  The 
glyco-proteins  are  compounds  of  a  protein  molecule  with  a  sub- 
stance, or  substances,  containing  a  carbohydrate  group.  In  solu- 
tion, they  are  characterized  by  being  ropy  and  mucilaginous  and 
are  contained  in  the  mucus  secretions  of  many  membranes  and 
glands  of  the  animal. 


218  Agricultural  Chemistry 

The  proteoses  and  peptones  are  found  in  the  digestive  tract  of 
the  animal  and  are  derived  from  the  proteins  of  the  food  by  the 
action  of  the  proteolytic  enzymes  of  the  alimentary  canal.  They 
are  water-soluble  bodies. 

All  of  these  protein  bodies  contain  very  .similar  amounts  of 
nitrogen — namely,  15  to  18  per  cent.  Besides  the  above  nitro- 
genous materials  constituting  tissue,  the  animal  juices  contain  a 
variety  of  nitrogenous  substances  such  as  creatin,  creatinin,  sar- 
cosine,  etc.,  but  with  which  we  are  not  concerned. 

The  ammo-acids  are  simple  nitrogenous  bodies  formed  during 
the  process  of  digestion  from  the  proteins  of  the  food  and  are  be- 
lieved to  be  the  building  materials  out  of  which  the  animal  re- 
constructs its  own  tissue  protein. 

The  amides,  principally  represented  by  urea,  CO(NH2)2,  in 
the  urine,  are  the  simple  nitrogenous  waste  products  of  the  tis- 
sues. In  the  cow,  85  to  95  per  cent  of  the  total  nitrogen  in  the 
urine  is  in  this  form. 

The  fats  occurring  in  the  animal  body  are  principally  stearin, 
palmitin  and  olein.  Stearin  predominates  in  hard  fats  and  olein 
in  more  fluid  fats.  They  are  identical  in  composition  with  these 
same  materials  described  in  the  chapter  on  the  plant.  Lecithin, 
a  complex  fat  containing  both  nitrogen  and  phosphorus,  is  also 
widely  distributed  in  animal  tissue. 

Carbohydrates.  The  important  carbohydrate  of  the  animal 
body  is  glycogen,  (C6H1005)n,  found  in  considerable  quantities 
in  the  liver  and  in  smaller  amounts  in  the  muscular  tissue.  It 
resembles  starch  in  its  constitution.  At  no  time  does  it  constitute 
an  appreciable  proportion  of  the  animal's  weight.  In  this  re- 
spect animals  differ  from  plants.  In  the  latter  the  stored  re- 
serve material  is  usually  starch,  while  in  the  animal,  fat  is  the 
reserve  material.  The  glycogen  found  in  animal  tissue  has  had 
its  origin  from  the  various  carbohydrates  of  the  feed.  These 
have  been  absorbed  from  the  digestive  tract  largely  in  the  form 
of  dextrose,  one  of  the  simpler  sugars,  and  from  which  glyeogen 
has  been  rebuilt. 

Composition  of  farm  animals.     The  amounts  of  water,  nitro- 


The  Animal  Body 


219 


genous  matter,  fat  and  ash  constituents  present  in  a  large  num- 
ber of  animals,  have  been  determined  by  Lawes  and  Gilbert  at 
the  Rothamsted  Station.  The  following  table  shows  the  per- 
.  centage  composition  of  the  whole  bodies  of  various  farm  animals. 
The  fat  pig  was  one  grown  for  fresh  pork,  not  for  bacon.  Store- 
animals  are  those  in  good  flesh,  but  not  fat. 

Composition  of  Farm  Animals 


Animal 

Water 

Fat 

Protein 

Ash 

Content  of 
stomach, 
etc. 

Fat  cal  f  

Per  cent 
63.0 

Per  cent 
14.8 

Per  cent 
15.2 

Per  cent 
3.8 

Per  cent 
3.2 

Half  fat  ox  

51.5 

19.1 

16.6 

4.6 

8  2 

Fat  ox  

45.5 

30.1 

14.5 

3.9 

6  0 

Fat  lamb  

47  8 

28  5 

12.3 

2.9 

8  5 

Store  sheep  

57.3 

18.7 

14.8 

3.2 

6.0 

Half  fat  sheep    .... 

50  2 

23  5 

14  0 

3  2 

9  1 

Fat  sheep  

43.4 

35.6 

12  2 

2  8 

6  0 

Store  pig    

55  1 

23  3 

13  7 

2.7 

5  2 

Fat  pie  .  . 

41  3 

42.2 

10.9 

1  6 

4  0 

It  will  be  noticed  that  in  nearly  every  case  water  is  the  largest 
ingredient  of  the  animal  body.  The  proportion  of  water  is  great- 
est in  young  and  lean  animals  and  diminishes  toward  maturity 
and  especially  during  fattening.  The  proportion  of  nitrogenous 
matter  and  ash  tends  to  increase  as  the  animal  ages,  but  dimin- 
ishes during  fattening.  The  half  fat  ox  contains  6  per  cent  more 
water  than  the  fat;  the  store  sheep  14  per  cent  more  than  the 
extra  fat,  and  the  store  pig  14  per  cent  more  than  the  fat.  The 
fattening  process  does  not  involve  a  replacement  of  the  water 
already  in  the  tissues,  but  the  increase  is  much  more  largely  dry 
matter.  Because  this  increase  during  fattening  is  largely  fat, 
the  proportion  of  protein  and  ash  in  the  dry  substance  of  the 
fattened  animal  has  decreased  relatively. 

The  largest  proportion  of  nitrogenous  matter  and  ash  are 
found  in  the  ox,  the  smallest  in  the  pig.  The  difference  in  the 


220 


Agricultural  Chemistry 


proportion  of  ash  is  chiefly  due  to  the  wide  difference  in  the  pro- 
portion of  bone  in  these  two  animals.  Fat  is  found  in  greatest 
quantity  in  the  pig  and  is  least  in  the  ox. 

The  following  table  shows  the  quantity  of  nitrogen  and  the. 
principal  ash  constituents  in  the  fasted  live  weight  of  the  animals 
analyzed  at  Rothamsted.  The  table  is  based  upon  a  weight  of 
1000  pounds  for  each  animal.  The  table  also  includes  milk,  wool 
and  eggs,  and  supplies  information  as  to  the  loss  a  farm  would 
sustain  by  the  sale  of  animal  products.  According  to  this  table, 
the  ox  contains,  in  proportion  to  its  weight,  a  larger  amount  of 
nitrogen  and  a  much  larger  amount  of  lime  and  phosphoric  acid 
than  either  the  sheep  or  pig.  Of  all  the  animals  raised  on  the 
farm,  the  pig  contains  the  least  of  all  the  important  ash  con- 
stituents. 

Attention  should  be  called  to  the  large  amount  of  potash  in 
unwashed  wool.  It  is  possible  for  the  fleece  to  contain  more 
potash  than  the  whole  body  of  the  shorn  sheep.  The  fleeces  of 
four  Hampshire  Down  sheep,  analyzed  at  Rothamsted,  contained 
about  6.5  per  cent  of  nitrogen  and  2  to  3  per  cent  of  ash. 

Ash  Oonstttuents  and  Nitrogen  in  1,000  Pounds  of  Various  Animals  and 
the  Same  Weight  of  Their  Products 


Phos- 

Animal 

Nitrogen 

phoric 

Potash 

Lime 

Magnesia 

acid 

Lbs. 

Lbs. 

Lbs. 

Lbs. 

Lbs. 

Fat  calf  

24.6 

15.3 

2.0 

16.4 

0.8 

Half  fat  ox  

27.4 

18.3 

2.0 

21.1 

0.8 

Fat  ox  

23.2 

15.5 

1.7 

17.9 

0.6 

Fat  iamb  

19.7 

11.2 

1.6 

12.8 

0.5 

Store  pheep  

23.7 

11.8 

1.7 

13.2 

0.5 

Fat  sheep  

19.7 

10.4 

1.5 

11.8 

0.5 

Store  pig  

22.0 

10.6 

1.9 

10.8 

0.5 

Fat  pig  

17.6 

6.5 

1.4 

6.3 

0.3 

Wool  (unwashed)... 

54.0 

0.7 

56.2 

1.8 

0.4 

Wool  (washed)  

94.4 

1.8 

1.9 

2.4 

0.6 

Milk  

5.7 

2.0 

1.7 

1.7 

0.2 

20.0 

4.2 

1.7 

60.8 

1.0 

The  Animal  Body 


221 


Fattening  an  animal  increases  the  proportion  of  butcher's 
meat  while  at  the  same  time  it  materially  modifies  its  composition. 
Jordan  gives  the  proportion  of  dressed  carcass  in  per  cent  as 
follows : 

Ox  Sheep  Swine 

Lean  animal  47        .  45  73 

Fat  animal   60  53  82 

The  composition  of  the  increase  of  an  animal  varies  much  un- 
der different  circumstances.  The  increase  of  a  young  growing 
animal  will  contain  much  water,  protein  and  ash;  that  of  a  ma- 
ture fattening  animal  will  consist  chiefly  of  fat.  From  this  it 
follows  that  a  larger  proportion  of  protein  and  ash  is  needed 
during  the  earlier  periods  of  growth ;  but,  because  of  the  larger 
proportion  of  water,  a  smaller  amount  of  food  is  required  to 
produce  one  pound  of  gain. 

The  composition  of  the  increase  of  oxen,  sheep  and  pigs,  when 
passing  from  the  "store"  to  the  "fat"  condition  has  been  cal- 
culated by  Lawes  and  Gilbert. 

Percentage  Composition  of  the  Increase  While  Fattening 


Water 

Protein 

Fat 

Ash 

Sheep  .  . 

Per  cent 
22.0 

Per  cent 
7.2 

Per  cent 
68.8 

Per  cent 
2.0 

Oxen  

24.6 

7.7 

66.2 

1.5 

Pigs.. 

28.6 

7.8 

63.1 

0.5 

Average  

25.1 

7.6 

66.0 

1.3 

The  increase  during  the  fattening  stage  of  growth  is  seen  to 
contain  8  to  9  parts  of  fat  for  one  of  nitrogenous  matter. 

Important  parts  of  the  animal  body.  Blood  consists  of  a 
colorless  liquid — plasma — holding  in  suspension  numerous  small 
solid  bodies,  the  red  and  white  corpuscles.  The  red  corpuscles 
give  the  blood  its  characteristic  color.  These  corpuscles  have  a 


Agricultural  Chemistry 

definite  structure  and  make  up  30  to  40  per  cent  of  the  blood. 
When  taken  from  an  animal  the  plasma  quickly  deposits  one  of 
its  protein  constituents,  fibrin,  which,  entangling  the  corpuscles, 
•causes  them  to  separate  as  a  clot  from  the  yellowish  liquid — the 
serum.  Blood  plasma  is  therefore  the  liquid  portion  of  fresh 
blood,  while  blood  serum  is  the  liquid  portion  after  clotting.  The 
latter  differs  from  the  former  by  having  lost  its  fibrin  and  a 
portion  of  its  lime,  magnesia  and  phosphoric  acid. 

Blood  is  the  nutrient  fluid  of  the  body.  It  is  the  source  of 
nourishment  for  all  the  cells.  Out  of  its  ingredients  the  tissues 
are  built.  It  contains  about  81  per  cent  of  water,  so  that  it 
easily  holds  in  solution  whatever  soluble  nutrients  are  furnished 
it  from  the  digestive  tract. 

The  19  per  cent  of  solids  consists  of  the  following  materials: 
10  per  cent  of  haemoglobin ;  7  per  cent  of  proteins ;  about  1  per 
-cent  of  ash;  the  remaining  1  per  cent  consists  of  fats,  sugars, 
lecithin,  etc.  The  color  of  the  blood  is  due  to-  haemoglobin.  This 
body  is  extremely  complex  in  composition  and  contains  about 
0.4  per  cent  of  iron.  Haemoglobin  is  a  dark  purplish-red  colored 
substance.  It  readily  combines  with  oxygen  to  an  oxy-compound 
which  is  bright  red  in  color.  The  haemoglobin  plays  an  import- 
ant part  in  respiration  as  the  carrier  of  oxygen  to  the  tissues. 

The  red  corpuscles  consist  of  circular,  bi-concave  discs,  though 
their  shape  and  size  vary  in  different  animals.  They  are  largest 
in  reptiles.  In  man  the  average  diameter  of  a  blood  corpuscle  is 
about  1/3200  of  an  inch,  and  its  thickness  about  1/12800  of  an 
inch.  These  corpuscles  contain  the  haemoglobin,  the  coloring 
matter  of  the  blood.  When  they  are  treated  with  water  or  ether 
they  loose  their  coloring  matter  and  leave  a  nitrogenous  residue 
which  retains  the  shape  of  the  original  corpuscles. 

Bones  consist  of  an  earthy  frame  work  composed  mainly  of 
calcium  phosphate,  permeated  by  an  albuminoid,  called  ossein, 
and  by  nerves,  blood  vessels,  etc.  In  the  hollow  center  of  many 
bones  is  the  marrow,  which  consists  of  fats  and  proteins.  The 
relative  proportion  of  mineral  and  organic  matter  in  bones  varies 


The  Animal  Body  223 

considerably.  The  amount  of  mineral  matter  in  the  green  bone 
varies  from  40  to  60  per  cent.  No  definite  percentage  can  be 
.given,  as  the  amount,  up  to  a  certain  limit,  will  vary  with  the 
supply  of  lime  and  phosphoric  acid  in  the  food  and  also  with  the 
source  of  the  bone. 

The  ash  of  bone  is  not  entirely  phosphate  of  lime,  but  contains 
in  addition  carbonates,  fluorides,  chlorides  and  magnesia.  The 
following  analysis  of  bone  ash  is  given  by  Ingle : 

Calcium  phosphate  86.0  per  cent 

Magnesium   phosphate    1.0         " 

Calcium,  as  carbonate,  chloride  and  fluoride  7.3        " 

Carbon  dioxide    G.2         " 

Chlorine    0.2         " 

Fluorine 0.3         " 

Muscular  tissue  consists  largely  of  proteins  and  water,  but 
contains  in  addition  small  quantities  of  fat,  glycogen  (animal 
starch),  and  certain  nitrogenous  extractives,  such  as  creatin, 
€4H9N202,  creatinin,  C4H7N20,  xanthin,  CSH4N402,  and  guanin, 
C5H3N50.  Small  quantities  of  dextrose  are  also  contained  in 
muscle  tissue.  The  ash  of  muscle  consists  largely  of  potash  and 
phosphoric  acid  compounds,  but  there  are  also  present  small 
amounts  of  sodium,  magnesium,  calcium,  chlorine  and  iron. 
Muscle  u-s-ually  contains  about  75  to  80  per  cent  of  water,  and  20 
to  25  per  cent  of  solids. 

"When  a  muscle  does  work,  the  glycogen  and  sugar  are  burned 
at  an  increased  rate  and  the  blood,  which  bathes  the  muscle,  re- 
ceives an  increased  proportion  of  carbon  dioxide.  Fats  are  also 
sources  of  mechanical  work  for  the  muscle.  When  fats  and  car- 
bohydrates are  available  for  consumption,  the  nitrogenous  waste 
of  the  muscle  is  not  increased  by  exercise,  and  only  the  normal 
amount  of  waste  nitrogenous  products,  as  urea,  uric  acid,  etc., 
appear  as  the  result  of  the  life  processes. 

Fatty  tissue  is  made  up  of  relatively  large,  oval,  or  spherical 
cells.  These  cells  consist  of  a  nitrogenous  membrane,  filled  with 
fat,  ivhich  during  life  is  fluid.  The  fats,  which  resemble  in  con- 
stitution the  vegetable  oils  already  described,  are  chiefly  com- 


224  Agricultural  Chemistry 

posed  of  stearin,  palmitin  and  olein.  The  fat  cells  may  be  found 
deposited  between  the  fibers  or  cells  of  muscular  tissue,  or  may 
constitute  almost  the  entire  mass  of  adipose  tissue.  When  the 
latter  is  the  case,  the  fatty  tissues  will  consist  of  water,  membrane 
and  fat  in  about  the  following  proportions: — 

Ox  Sheep  Pig 

Water        (per   cent) 9.96  10.48  6.44 

Membrane         "          1.16  1.64  1.35 

Fat                       "           88.88  87.88  92.21 

Fat  is  stored  in  the  body  as  a  reserve  material  from  which  the 
animal  can  draw  in  time  of  scarcity  of  food.  It  is  the  most  con- 
centrated form  in  which  energy  is  stored  in  the  animal. 

Connective  tissue,  of  which  tendons,  ligaments,  cartilage  and 
skin  are  mainly  composed,  consists  of  substances  which  yield 
gelatine  when  heated  with  water.  These  are  the  albuminoid  com- 
pounds and  constitute  the  framework  of  the  animal  tissues.  They 
are  to  the  animal  body  what  cellulose-  is  to  the  vegetable  kingdom. 
They  are  only  slightly  attacked  by  acids  and  alkalies  and  are  in- 
soluble in  water  and  salt  solutions.  Several  different  bodies  have 
been  recognized,  among  which  are  elastin,  collagen  and  keratin. 
The  first  is  the  principal  constituent  of  the  elastic  tissues  and 
contains  but  traces  of  sulphur.  The  second,  collagen,  constitutes 
the  foundation  of  cartilage  and  may  be  extracted  from  these  tis- 
sues with  hot  water.  The  product  which  goes  into  solution  is 
called  gelatine  and  solidifies  on  cooling.  It  contains  about  0.6 
per  cent  of  sulphur.  The  third  substance,  keratin,  is  the  main 
constituent  of  hair,  horn,  hoof,  feathers  and  wool,  and  contains 
4  to  5  per  cent  of  sulphur.  It  is  insoluble  in  water,  but  by  heat- 
ing with  water  under  pressure  to  150-200°  C.  it  may  be  ren- 
dered soluble  and  then  constitutes  glue. 

Processes  of  nutrition.  "We  have  seen  that  the  food  of  plants 
is  of  the  simplest  character  and  from  such  simple  materials  as 
carbon  dioxide,  nitrates,  certain  other  inorganic  salts  and  water, 
a  plant  is  able  to  construct  a  great  variety  of  complex  compounds. 
It  accomplishes  these  surprising  transformations  by  a  consump- 


The  Animal  Body  225 

tion  of  energy  (sunlight)  external  to  itself.  An  animal  has  no 
such  power.  The  animal  tissues  are  built  up  from  the  complex 
substances  existing  ready-formed  in  the  food.  The  animal  de- 
rives no  aid  from  external  energy.  The  temperature  of  the  ani- 
mal body  (about  100°  F.)  is  maintained  by  heat  generated  within 
the  body  and  by  the  combustion  of  the  material  consumed  as  food. 
The  energy  by  which  all  the  mechanical  work  of  the  animal  is 
performed,  comes  from  the  same  source.  The  source  of  heat  and 
force  in  the  animaJ  is  thus  purely  internal. 

It  is  apparent  from  what  has  been  said  that  the  food  of  animals 
has  duties  to  perform  which  are  not  demanded  of  the  food  of 
plants.  In  plants  the  food  chiefly  provides  material  for  build- 
ing up  the  vegetable  tissues.  In  the  animal,  besides  constructing 
tissue,  the  food  must  furnish  the  means  of  producing  heat  and 
performing  mechanical  work;  to  accomplish  this  result,  it  must 
be  burned  in  the  animal  body. 

Functions  of  food  constituents.  The  solid  ingredients  of 
vegetable  food  may  be  classed,  as  (1)  proteins;  (2)  fats;  (3)  car- 
bohydrates ;  (4)  salts.  Besides  these  general  classes  of  food  con- 
stituents, we  have  in  immature  vegetable  products,  as  hays,  roots, 
etc.,  a  fifth  class — the  amino-acids  and  amides — which  also  take 
part  in  animal  nutrition.  They  are  the  simple  intermediary  ni- 
trogenous substances,  formed  from  the  nitrates  absorbed  by  the 
plant,  and  eventually  take  part  in  the  construction  of  the  com- 
plex proteins  of  seeds  and  plant  tissue. 

The  proteins  occurring  in  seeds,  roots  and  other  forms  of 
vegetable  food,  have  a  general  similarity  in  composition  to  those 
found  in  milk,  blood,  and  flesh,  but  are  by  no  means  identical. 
From  the  proteins  of  the  food  are  formed  not  only  the  proteins  of 
the  soft  tissues  of  the  animal,  but  also  such  a  class  of  proteins  as 
the  albuminoids,  which  differ  so  materially  in  properties  from 
the  proteins  of  blood  and  muscle.  It  is  also  very  probable  that 
fat,  a  non-nitrogenous  body,  may  be  formed  from  protein.  This 
is  still  a  much  disputed  question  and  it  remains  for  future  in- 
vestigations to  decide  this  point  definitely. 


226  Agricultural  Chemistry 

Proteins  can  also  serve  as  a  source  of  energy.  In  the  case  of 
a  dog  eating  exclusively  a  meat  diet,  probably  a  greater  part  of 
the  protein  eaten  is  not  stored  but  is  used  as  fuel.  We  see  from 
this  that  the  proteins  can  serve  most  of  the  requirements  of  the 
animal,  a  statement  which  cannot  be  made  of  any  other  food 
constituent.  They  are  the  true  tissue  builders. 

An  animal,  even  when  not  increasing  in  weight,  will  always  re- 
quire a  certain  constant  supply  of  protein  in  its  food  to  replace 
the  waste  of  nitrogenous  tissue,  which  is  always  going  on  even 
during  rest.  The  cell  proteins  are  constantly  undergoing  decom- 
position and  reconstruction. 

"When  the  nitrogenous  tissues  of  the  animal,  or  the  proteins 
consumed  as  food  are  decomposed  in  the  body,  the  nitrogen  they 
contain  is  largely  excreted  in  the  form  of  a  simple  nitrogenous 
substance,  urea.  This  is  eliminated  by  way  of  the  kidneys  in  the 
urine.  There  are  small  quantities  of  other  nitrogenous  products, 
such  as  uric  acid,  creatin,  creatinin,  and  in  the  case  of  herbivora, 
hippuric  acid,  C6H5.CO.NH.CH2.COOH,  voided  in  the  urine,  but 
they  constitute  but  a  small  proportion  of  the  total  nitrogen  elim- 
inated. The  urea  produced  is  rich  in  nitrogen,  containing  about 
46.6  per  cent.  It  represents  about  one- third  the  weight  of  the 
protein  oxidized. 

The  amides  and  amino-acids  consumed  as  food  are  burned  in 
the  body  and  their  nitrogen  excreted  as  urea.  It  is  very  prob- 
able that  they  can,  in  part,  take  the  place  of  proteins  as  tissue 
builders.  In  addition,  by  their  combustion,  they  serve  as  sources 
of  heat  and  force. 

The  fats  are  free  from  nitrogen.  Those  contained  in  food  are 
similar  to  those  found  in  the  animal  body.  It  appears  possible 
for  a  vegetable  fat  to  become  deposited  in  the  animal  without 
essential  change.  Small  deposits  occur  in  every  organ  and  cell. 
The  fat  reserves  vary  much  in  size,  depending  on  nutritive  con- 
ditions, so  that  no  definite  statement  can  be  made  regarding  the 
fat  content  of  the  individual  organs.  The  fat  of  the  food  is 
either  burned  in  the  animal  system  to  furnish  heat  and  mechan- 


The  Animal  Body  227 

ical  energy  or  is  stored  up  as  reserve  material.  With  their  larger 
content  of  carbon  and  smaller  proportion  of  oxygen,  fats  are  less 
easily  oxidized  than  sugars  and  require  a  larger  intake  of  oxygen 
for  their  combustion;  but  when  oxidized  they  yield  more  heat 
per  pound  than  any  other  food  ingredient. 

The  carbohydrates  of  the  food  are  chiefly  starch,  sugars,  cel- 
luloses and  pentosans.  Various  other  non-nitrogenous  constit- 
uents of  food,  such  as  the  pectins,  lignin  and  vegetable  acids, 
are  generally  included  under  this  title,  though  they  are  not, 
strictly  speaking,  carbohydrates.  Carbohydrates  form  the  larg- 
est part  of  all  vegetable  food.  They  are  not  permanently  stored 
in  the  animal  body,  but  serve  when  burned  in  the  system,  for  the 
production  of  heat  and  mechanical  work.  If  a  fattening  steer 
were  consuming  16  pounds  of  digestible  organic  matter  and  gain- 
ing two  pounds  of  live  weight  daily,  the  body  increase  and  urine 
would  contain  not  over  2.5  pounds  of  dry  matter,  leaving  not  less 
than  13.5  pounds  to  be  oxidized,  of  which  12  pounds  might  con- 
sist of  carbohydrates  and  fat,  mostly  the  former. 

The  carbohydrates  are  also  capable,  when  consumed  in  excess 
of  immediate  requirements,  of  conversion  into  fat.  The  well- 
recognized  value  of  corn  meal  as  a  fattening  food,  a  feeding  stuff 
nearly  seven-tenths  of  which  consists  of  starch  and  similar  struc- 
tures, is  a  practical  illustration  of  this  truth. 

The  carbohydrates  and  fats  are  the  natural  fuel  food  stuffs  of 
the  body.  They  cannot  serve  for  the  renewal  or  upbuilding  of 
tissue, — except  fatty  tissue — but  by  oxidation  they  constitute  an 
economical  fuel  for  maintaining  body  temperature  and  for  power 
to  run  the  bodily  machinery.  Proteins  may  likewise  serve  as 
fuel,  but  this  is  apparently  confined  to  a  non-nitrogenous  part  of 
their  molecule.  "When  fats  or  carbohydrates  are  available  the 
proteins  of  the  tissue  are  not  normally  consumed  for  production 
of  heat  and  force.  Only  when  the  former  are  lacking  will  the 
animal  increase  its  protein  metabolism  and  nitrogen  output  for 
purposes  of  maintaining  the  body  temperature.  A  moderate 
quantity  of  protein  supplied  to  a  growing  animal  will  thus  pro- 


228  Agricultural  Chemistry 

duce  a  much  larger  increase  of  muscle  when  accompanied  by  a 
liberal  supply  of  carbohydrates  or  fats.  In  this  case,  the  non- 
nitrogenous  constituents  of  the  food  supply  the  demands  for  heat 
and  work  and  the  protein  can  be  devoted  to  the  rebuilding  or 
increase  of  tissue. 

If  an  adult  animal  receives  the  small  amount  of  protein  and 
salts  necessary  to  repair  the  daily  waste  of  tissue,  it  would  be 
expected  that  the  whole  of  the  remaining  wants  might  be  met  by 
supplying  carbohydrates  or  fats.  This  is  to  some  extent  true; 
but  a  ration  very  poor  in  protein  is  not  found  to  be  consistent 
with  real  bodily  vigor.  There  is  some  specific  action  of  proteins 
not  as  yet  understood.  They  appear  to  stimulate  cell  activity, 
a  property  not  possessed  by  fats  and  carbohydrates. 

The  ash  constituents  present  in  food  are  the  same  as  those 
found  in  the  animal  body.  The  animal  simply  selects  from  the 
digested  ash  constituents  those  of  which  it  is  in  need.  The  tis- 
sue, the  blood,  digestive  fluids,  and  the  bony  framework  contain  a 
variety  of  these  bodies,  which  are  as  essential  as  any  of  the  other 
substances  considered  for  the  building  and  maintenance  of  the 
animal  body.  Without  lime  and  phosphoric  acid  there  can  be  no 
bone  formation,  and  the  digestive  juices  would  cease  to  be  active 
if  deprived  of  chlorine.  A  cow  from  which  common  salt  is  with- 
held will,  in  time,  die.  Not  only  must  the  growing  calf  have  ash 
materials  for  constructive  purposes,  but  the  mature  ox  must  be 
supplied  with  them  in  order  to  sustain  the  nutritive  processes. 
The  milch  cow,  which  stores  combinations  of  lime,  phosphoric 
acid,  potash  and  other  salts  in  the  milk,  must  have  an  adequate 
supply  of  these  materials.  Nothing  else  can  take  their  place. 
Lime  and  phosphoric  acid,  stored  in  abundance  in  the  framework 
'of  the  animal,  may  at  times  of  deficient  supply  in  the  food,  act  as 
internal  sources ;  but  ultimately  all  ash  elements  must  have  been 
contained  in  the  food. 

Digestion.  We  have  accepted  so  far  without  discussion  the 
self-evident  fact  that  the  food  is  the  immediate  source  of  the 
energy  and  substance  of  the  animal  body.  It  is  now  necessary  to 


The  Animal  Body  229 

consider  the  way  in  which  the  nutrition  of  the  animal  is  accom- 
plished. Digestion  is  the  important  process  by  which  the  food 
of  an  animal  is  rendered  capable  of  being  absorbed  into  the  sys- 
tem and  utilized  in  building  up  or  renewing  the  tissue  of  the 
body.  Hay  and  grain  cannot  directly  be  transferred  to  the 
blood,  but  must  first  be  brought  into  soluble  and  diffusible  con- 
dition before  they  can  pass  out  of  the  alimentary  tract  into  the 
blood  and  lymph.  This  is  accomplished  partly  by  mechanical 
means,  but  mainly  by  chemical  changes,  which  are  produced 
chiefly  by  the  action  of  bodies  called  enzymes. 

Enzymes  are  a  peculiar  class  of  substances  produced  by  living 
cells.  They  are  of  unknown  composition  and  are  peculiar  in  that 
the  chemical  changes  which  they  induce  are  the  result  of  what  is 
called  catalysis,  or  contact.  That  is,  during  the  solution  of  the 
food  stuffs,  the  enzyme  is  not  used  up  or  destroyed,  but  by  its 
mere  presence  sets  in  motion  or  quickens  a  reaction  between  two 
other  substances.  For  example,  the  enzyme  of  the  saliva  causes 
the  starch  of  the  food  to  combine  with  water,  with  the  result  that 
the  soluble  sugar  maltose,  is  formed.  An  enzyme  that  acts  upon 
starch,  for  example,  cannot  act  on  proteins  or  fats.  Some  digest- 
ive fluids  have  the  power  of  producing  changes  in  different 
classes  of  food  stuffs,  but  when  this  occurs,  it  is  assumed  to  be 
due  to  the  presence  in  the  same  fluid  of  different  enzymes. 
Again,  enzymes  are  .sensitive  to  their  environment,  and  a  proper 
temperature  and  reaction  must  be  maintained  for  their  activity. 
The  activity  of  saliva  is  extremely  sensitive  to  the  nature  of  the 
reaction  and  ceases  when  that  becomes  acid.  Enzymes  are  thus 
seen  to  be  more  or  less  unstable  substances,  endowed  with  great 
power  as  digestive  agents,  but  sensitive  to  a  high  degree  and 
working  advantageously  only  under  definite  conditions. 

Digestion  in  the  mouth.  The  first  step  is  mastication,  by 
which  the  food  is  subdivided  and  crushed  by  the  action  of  the 
teeth  and  thoroughly  mixed  with  saliva.  This  special  secretion 
has  its  origin  in  several  secreting  glands,  and  from  these  this 
liquid  is  poured  into  the  mouth  through  ducts,  opening  in  the 


230  Agricultural  Chemistry 

cheek  under  the  tongue.  Saliva  is  a  highly  dilute  liquid  of  faintly 
alkaline  reaction  and  contains  an  enzyme,  ptyalin,  which  has  the 
power  of  bringing  about  the  same  changes  as  are  produced  by 
plant  diastase,  that  is,  the  conversion  of  starch  into  the  sugar, 
maltose,  thus: — 

2C6H1005+H20=C12H220U 
starch  maltose 

This  change  begins  in  the  mouth  and  continues  for  a  limited  time 
in  the  stomach,  or  until  the  gastric  secretions  establish  an  acid 
reaction  in  the  stomach  contents.  "When  this  is  established, 
salivary  digestion  ceases.  The  proteins  and  fats  are  not  attacked 
by  the  salivary  secretion. 

Ruminants,  whose  feed  usually  contains  much  starchy  material, 
secrete  enormous  quantities  of  saliva.  It  is  estimated  that  oxen 
and  horses  secrete  from  88  to  122  pounds  daily.  This  serves  the 
additional  important  function  of  properly  preparing  the  food 
for  swallowing. 

Gastric  digestion.  The  food  after  mastication  passes  down 
the  gullet  into  the  stomach.  In  the  case  of  the  horse  and  pig  the 
stomach  is  a  single  sac,  and  true  gastric  digestion  begins  at  once. 
In  ruminants,  as  the  ox  and  sheep,  the  stomach  consists  of  four 
divisions,  or  sacs,  and  not  until  the  fourth  is  reached,  does  gastric 
digestion  proper  begin.  These  sacs  may  be  considered  as  en- 
largements of  the  oesophagus  and  primarily  for  the  storage  of 
the  bulky  materials  consumed  by  these  classes  of  farm  animals. 
The  four  divisions  are  the  paunch,  honey-comb,  many-plies  and 
rennet,  or  what  the  anatomist  has  called  the  rumen,  reticulum, 
omasum  and  abomasum.  The  capacity  of  these  cavities  in  the 
ox  is,  on  the  average,  not  far  from  50  to  60  gallons,  about  nine- 
tenths  of  the  space  belonging  to  the  paunch.  It  is  in  the  paunch 
that  the  food  is  first  stored,  only  the  finer  portions  being  carried 
by  what  is  known  as  the  oesophagal  groove  to  the  third  stomach, 
and  finally  from  this  compartment  into  the  fourth  and  last  di- 
vision. From  the  paunch  the  food  is  returned  to  the  mouth 
where  it  is  more  finely  ground  before  passing  to  the  fourth  stom- 


The  Animal  Body 


231 


ach  for  digestion.  This  is  what  is  termed  "chewing  the  cud." 
In  the  paunch  salivary  digestion  probably  continues,  as  well  as 
other  fermentations  induced  by  various  micro-organisms.  Here 
possibly  a  partial  fermentation  of  cellulose  by  bacterial  enzymes 
begins. 

When  the  food  reaches  the  fourth  stomach,  it  meets  with  the 
characteristic  secretion  of  that  organ,  the  gastric  juice.  This 
juice  is  secreted  by  glands  located  in  the  mucus  membrane  of 
the  stomach.  It  is  a  watery  fluid,  containing  various  salts,  as 
chlorides  and  phosphates  of  calcium,  magnesium,  sodium  and 
potassium,  free  hydrocUoric  acid  and  the  two  enzymes,  pepsin 
and  rennin.  The  combination  of  pepsin  and,  the  acid  is  the  ef- 


On  the  left— stomach  of  the  horse.  A,  end  of  the  oesophagus;  B,  pylorlc 
end,  or  beginning  of  the  intestine.  On  the  right — stomach  of  the 
sheep.  O,  oesophagus;  P,  rumen;  R,  reticulum;  F,  omasum; 
C,  abomasum;  I,  commencement  of  the  small  intestine;  1,  oeso- 
phagal  groove;  2,  opening  between  omasum  and  abomasum. 

fective  agent  in  the  digestion.  They  are  secreted  by  different 
gland  cells  in  the  stomach  walls  and  the  amount  of  hydrochloric 
acid  secreted  during  24  hours  by  a  normal  man,  under  ordinary 
conditions  of  diet,  amounts  to  what  would  constitute  a  fatal  dose 


232  Agricultural  Chemistry 

of  acid,  if  taken  at  one  time  in  concentrated  form.  The  main 
action  of  gastric  juice  is  exerted  on  the  proteins  of  the  food, 
which  under  its  influence,  are  gradually  dissolved  and  converted 
into  soluble  products,  known  as  proteoses  and  peptones.  This 
enzyme,  like  the  ptyalin  of  the  saliva,  is  influenced  by  tem- 
perature, maximum  digestive  action  being  manifested  at  about 
38°  C.,  the  temperature  of  the  body.  Further,  a  certain  degree 
of  acidity  is  essential  for  procuring  the  highest  degree  of  ef- 
ficiency. Pepsin  acts  best  in  the  presence  of  from  0.1  to  0.3  per 
cent  of  free-  hydrochloric  acid.  It  is  said  that  the  gastric  juice 
of  the  sheep  has  a  low  acidity,  while  that  of  the  dog  has  the  high- 
est recorded  among  mammals. 

Chemically,  the  results  are  the  same  in  the  stomachs  of  all  farm 
animals,  that  is,  the  proteins  are  changed  to  the  soluble  forms 
-known  as  proteoses  and  peptones.  The  utilization  of  coarse  fod- 
der by  the  horse  is  not  as  complete  as  in  the  ox  for  the  reason 
that  in  the  case  of  the  former  there  is  no  preliminary  remastica- 
tion  and  trituration  before  the  food  material  comes  in  contact 
with  the  gastric  juice. 

Another  important  function  of  gastric  juice  is  that  of  curdling 
milk,  due  to  the  presence  in  the  secretion  of  the  peculiar  enzyme 
known  as  rennin.  This  is  present  in  the  stomach  of  all  mammals 
and  it  is  the  calf's  active  secretion,  which  is  the  source  of  com- 
mercial rennet  used  in  cheese  making.  The  purpose  of  this 
enzyme  can  only  be  conjectured.  As  the  sole  nutriment  of  the 
young,  milk  occupies  a  peculiar  position  as  a  food  stun2,  and  be- 
ing a  liquid,  its  protein  constituents  might  easily  escape  complete 
digestion  were  it  to  pass  too  hastily  through  the  digestive  tract. 
Experiments  have  shown  this  to  be  true  of  liquid  foods.  But 
when  curdled  by  the  rennin,  the  proteins  of  the  milk  in  their 
clotted  state,  must  remain  for  a  longer  time  in  the  stomach,  and 
their  partial  digestion  by  gastric  juice  made  certain. 

Among  other  factors  in  gastric  digestion,  the  muscular  move- 
ments of  the  stomach  walls  are  to  be  emphasized,  since  we  have 
here  a  mechanical  aid  to  digestion  of  no  small  moment  and  like- 


The  Animal  Body  233 

wise  a  means  of  accomplishing  the  onward  movement  of  the 
stomach  contents.  From  the  stomach  but  little  absorption  of  the 
soluble  food  materials  takes  place.  It  is  in  the  intestine  that  both 
digestion  and  absorption  are  at  their  best. 

Digestion  in  the  intestine.  "When  the  food  leaves  the  stomach 
it  enters  the  small  intestine.  At  this  point  it  is  only  partially 
digested.  The  fats  of  the  food  have  not  as  yet  been  changed, 
and  undoubtedly  a  considerable  proportion  of  the  proteins  and 
carbohydrates  susceptible  to  solution  is  still  to  be  acted  upon. 
Immediately  after  passing  from  the  stomach,  the  partially  di- 
gested mass  comes  in  contact  with  the  pancreatic  juice,  the  bile 
and  intestinal  juice,  and  the  changes  which  began  in  the  mouth 
and"  stomach,  together  with  others  which  set  in  for  the  first  time, 
proceed  at  a  vigorous  rate.  The  bile  is  secreted  by  the  liver  and 
stored  in  the  small  sac  attached  to  that  organ  and  called  the 
gall  bladder  and  from  which  it  is  brought  to  the  intestine  by  a 
duct  opening  near  the  orifice  leading  out  of  the  stomach.  Bile 
is  a  reddish-yellow  (in  carnivorous  animals)  or  green  (in  herb- 
ivora)  liquid,  with  an  alkaline  reaction  and  bitter  taste.  It  con- 
tains complex  salts,  which  in  conjunction  with  the  fat  splitting 
enzyme  of  the  pancreatic  juice,  reduces  the  fats  to  an  emulsion, 
a  form  in  which  they  can  be  absorbed  into  the  blood.  When  bile 
is  prevented  from  entry  into  the  intestine,  the  fat  of  the  food 
largely  passes  out  in  the  feces.  Besides  this  important  relation 
to  fat  digestion,  the  bile  also  acts  in  some  degree  as  an  anti- 
septic, preventing  putrefaction  in  this  part  of.  the  intestine. 

The  pancreatic  juice  is  of  strongly  alkaline  reaction  due  to  its 
content  of  sodium  carbonate,  and  is  characterized  by  the  pres- 
ence of  at  least  three  distinct  enzymes ;  these  are  trypsin,  a  pro- 
tein digesting  ferment ;  lipase,  a  fat  splitting  enzyme ;  and  amy- 
lopsin,  a  starch  digesting  enzyme.  This  juice  comes  from  the 
pancreas  and  enters  the  intestine  through  a  small  duct,  which 
in  some  animals  is  confluent  with  the  bile  duct.  By  the  action  of 
this  juice,  the  acid  chyme  from  the  stomach  is  rapidly  converted 
into  an  alkaline  mass  and  the  enzyme  pepsin  is  quickly  destroyed 


234  Agricultural  Chemistry 

in  the  new  environment.  Trypsin,  effective  in  alkaline  media, 
now  continues  the  protein  digestion,  splitting  the  proteoses  and 
peptones,  as  well  as  unattacked  proteins,  into  simpler  structures. 
In  this  act  it  is  aided  by  another  enzyme,  known  as  erepsin,  se- 
creted by  the  mucus  membrane  of  the  intestine.  These  two 
enzymes  are  powerful  agents  and  under  their  combined  action 
the  proteins  are  reduced,  in  part  at  least,  to  simple  fragments, 
the  amino-acids,  thus: — 

Native  protein 

Meta  protein 

I 
Proteosea 

I 
Peptones 

J         I  ; 

Poly-peptides    Amino  acids 

The  fatty  foods  undergo  little  or  no  alteration  until  they  reach 
the  intestine.  "While  in  the  stomach  they  become  liquid  from 
the  heat  of  the  body  and  the  neutral  fat  is  liberated  from  the 
cell  structures  by  the  action  of  the  gastric  juice.  Most  of  the 
neutral  fats  must  be  decomposed  into  the  fatty  acids  and  gly: 
cerine,  of  which  they  are  composed,  before  absorption  into  the 
blood  can  take  place.  Under  the  influence  of  the  fat  splitting 
enzyme  of  the  pancreatic  juice,  lipase,  and  the  bile  salts,  the 
neutral  fats  are  partly  decomposed,  with  formation  of  soaps. 
These  soaps  aid  in  the  formation  of  an  emulsion  of  the  rest  of 
the  fats.  Such  an  emulsion  is  really  a  suspension  of  the  fat  in 
a  very  finely  divided  condition.  Soap,  free  acid  and  glycerine 
are  then  absorbed  from  the  intestine  and  are  found  again  com- 
bined in  the  lymph  as  neutral  fat.  In  this  way  the  fats  are  ren- 
dered available  for  the  nourishment  of  the  body. 

The  transformation  of  starch  into  maltose  is  again  taken  up 
by  the  amylopsin  of  the  pancreatic  juice.  The  maltose  is  further 
exposed  to  an  enzyme  of  the  intestinal  juice,  termed  maltase, 


The  Animal  Body  235 

and  decomposed  into  the  simple  sugar,  dextrose.  Other  carbo- 
hydrates, as  the  lactose  of  milk,  and  cane  sugar,  meet  with  special 
enzymes  in  the  intestinal  juice,  capable  of  converting  them  into 
simple  sugars,  the  final  form  in  which  the  carbohydrates  are 
absorbed  as: — 

C12H22011-(-H20=C6H1206-f-C6H1206 
cane  sugar  dextrose      levulose 

No  special  enzymes  fermenting  the  celluloses  and  pentosans, 
which  constitute  a  large  proportion  of  hays  and  straws,  have  as 
yet  been  prepared  from  the  normal  secretions  of  the  intestinal 
tract.  Possibly  their  partial  solution  is  effected  by  bacterial  fer- 
ments and  other  low  forms  of  life.  Such  solution  may  have  its 
beginning  in  the  paunch,  where  active  fermentations  are  in 
progress,  and  continue  in  the  lower  portions  of  the  digestive  tract. 

Absorption  of  food.  In  the  ways  mentioned  above,  the  pro- 
teins, fats  and  carbohydrates  of  the  food  are  gradually  digested. 
Throughout  the  length  of  the  small  intestine  absorption  proceeds 
rapidly ;  water,  salts  and  the  products  of  digestion  pass  out  from 
the  intestine  into  the  circulating  lymph  and  blood.  There  are 
two  pathways  by  which  absorbed  material  reaches  the  blood.  In 
the  intestinal  wall  are  numerous  projections,  called  villi.  Im- 
bedded in  these  structures  are  the  minute  branches  of  two  sys- 
tems of  vessels.  One  set  is  the  lacteals,  belonging  to  the  lym- 
phatic system  and  the  other  the  capillaries  of  the  blood  system. 
Materials  passing  into  the  lacteals  reach  the  thoracic  duct  and  by 
it,  in  a  roundabout  way,  are  carried  into  one  of  the  main  blood- 
vessels at  the  neck.  As  a  general  truth  it  may  be  stated  that  the 
fats  are  largely  absorbed  through  this  channel,  and  it  is  import- 
ant to  observe  that  when  they  reach  the  lacteals  they  are  again 
in  the  form  of  neutral  fats. 

Materials  absorbed  by  the  capillaries  of  the  blood  system  are 
carried  directly  to  the  liver  through  the  portal  vein,  and  there 
subjected  to  the  action  of  that  organ  before  they  enter  the  gen- 
eral circulation.  Most  salts  and  the  carbohydrates  and  proteins 
follow  this  course.  In  the  liver  the  soluble  sugars  are  converted 


236  Agricultural  Chemistry 

into  glycogen,  the  animal  starch,  and  as  such  temporarily  stored. 
The  amount  of  sugar  in  the  blood  is  a  constant  but  small  quan- 
tity and  as  this  is  required  in  the  tissue,  the  glycogen  is  recon- 
verted back  into  soluble  sugar  to  maintain  the  supply  in  the 
blood. 

The  fragments  of  protein  digestion,  the  proteoses,  peptones  and 
amino-acids,  are  in  part  found  as  .such  in  the  blood  and  serve  to 
nourish  the  cells  directly.  But  a  portion  of  these  fragments,  in 
passing  through  the  intestinal  wall,  or  after  reaching  the  liver, 
are  reconstructed  into  complex  proteins  before  being  cast  loose 
into  the  circulatory  system.  These  reconstructed  proteins  are 
the  serum  albumin,  serum  globulin  and  haemoglobin  of  the  blood, 
which  also  serve  as  sources  of  protein  for  the  various  body  tissues. 
The  processes  of  absorption  and  blood  regulation  are  wonderfully 
and  delicately  balanced  and  are  by  no  means  completely  under- 
stood. 

Feces.  The  portion  of  the  food  which  has  escaped  solution 
and  absorption,  together  with  certain  substances  already  absorbed 
but  re-excreted  by  way  of  the  intestines,  constitute  the  feces. 
Epithelial  cells  from  the  intestinal  walls,  parts  of  the  digestive 
juices,  bile,  bacterial  cells,  etc.,  will  make  up  a  large  portion  of 
the  fecal  matter. 

Respiration.  The  nutrients,  prepared  by. the  various  proc- 
esses of  solution  and  reconstruction  in  the  intestines  and  intesti- 
nal walls,  enter  the  blood  on  its  return  to  the  heart,  coming  into 
the  venous  circulation  by  way  of  the  thoracic  duct  and  liver 
(hepatic  vein),  as  already  described.  By  this  route,  the  blood, 
laden  with  nutrients,  passes  to  the  right  side  of  the  heart.  It  is 
then  carried  to  the  lungs,  by  way  of  the  right  ventricle,  to  be  re- 
turned to  the  left  side  of  the  heart,  and  from  which  it  is  pumped 
to  all  parts  of  the  body.  In  the  lungs  the  blood  is  supplied  with 
oxygen.  The  purple  of  venous  blood  is  changed  to  a  scarlet,- due 
to  the  absorption  of  oxygen  by  the  haemoglobin,  with  the  forma- 
tion of  oxy-haemoglobin,  the  important  oxygen  carrier  of  the 
blood.  At  the  same  time,  a  considerable  quantity  of  carbon 


The  Animal  Body  237 

dioxide,  most  of  which  was  in  solution  in  the  blood  plasma,  pos- 
sibly as  a  bi-carbonate,  is  given  up  to  the  air  within  the  lungs. 

Inspired  air  contains  about  21.0  per  cent  of  oxygen  and  .03 
per  cent  of  carbon-dioxide,  while  expired  air  carries  approxi- 
mately 16.5  per  cent  of  oxygen  and  4.4  per  cent  of  carbon-diox- 
ide. Though  the  absorption  of  oxygen  takes  place  in  the  lungs, 
it  is  not  there  that  the  processes  of  combining  the  oxygen  with 
the  carbon  and  hydrogen  of  'the  body  tissues  takes  place.  The 
blood,  through  the  haemoglobin  of  the  red-blood  corpuscles,  acts 
as  a  carrier  of  oxygen  and  the  actual  combustion  of  the  products 
derived  from  the  food  occurs  in  the  tissues  themselves.  The  rate 
of  combustion  in  the  tissues  is  a  variable  one,  dependent  upon 
the  amount  of  work  the  animal  is  doing  and  the  temperature  to 
which  it  is  exposed.  And  it  is  through  this  oxidation  of  the 
nutrients  in  the  cells  of  the  body  that  heat  and  mechanical  work 
are  produced. 

Elimination.  As  has  already  been  noted,  the  undigested  resi- 
dues of  food,  together  with  certain  excretory  products  eliminated 
by  way  of  the  intestines,  constitute  the  feces. 

The  products,  which  result  from  the  metabolism  of  the  body 
cells,  or  of  the  food  consumed,  are  removed  from  the  body  by  the 
lungs,  the  kidneys,  the  skin  and  the  intestine.  The  carbohy- 
drates and  fats,  which  are  oxidized  in  keeping  up  the  animal  heat 
or  in  furnishing  energy,  are  broken  down  into  carbon-dioxide 
and  water  and  removed  as  such  from  the  blood  by  the  lungs,  and 
to  a  smaller  extent  by  the  skin.  Water  and  salts  are  removed  by 
both  intestine  and  kidney,  while  the  perspiration  may  also  serve 
to  carry  considerable  quantities  of  these  materials.  The  elimina- 
tion of  the  products  of  protein  degradation  in  the  tissues  is  al- 
most entirely  by  way  of  the  kidneys.  The  larger  part  of  the 
nitrogen  is  eliminated  in  the  form  of  the  simple  body,  urea. 
There  are  other  forms  of  nitrogen  occurring  in  the  urine,  such 
as  uric  acid,  C5H4N403,  creatin,  C4H9N2O2,  creatinin,  C4H7N2O, 
ammonia,  etc.,  but  they  constitute  only  a  small  proportion  of  the 
total  nitrogen  eliminated. 


238  Agricultural  Chemistry 

The  sulphur  of  the  protein  molecule  is  also  removed  as  sulphate 
through  the  kidney,  while  the  phospJwrus  passes  out  of  the  body 
in  the  form  of  phosphates  by  both  the  intestines  and  kidney;  by 
far  the  larger  proportion  is  removed  through  the  intestine  in  the 
herbivora. 

The  quantity  of  nitrogen  in  the  urine  is  taken  as  a  measure  of 
the  amount  of  protein  decomposition  in  the  tissue.  This  may  be 
only  partly  true.  It  is  now  believed  that  a  considerable  part  of 
the  nitrogen  of  ingested  protein  has  not  been  built  into  body 
tissue,  but  is  eliminated  from  the  protein  molecule  as  ammonia 
in  the  intestine,  carried  to  the  liver,  and  from  there  finally  ex- 
creted through  the  kidney  as  urea.  The  carbonaceous  part  of 
the  protein  molecule  from  which  this  nitrogen  has  been  removed 
may  now  be  used,  through  combustion,  as  a  source  of  energy  for 
the  animal  body. 

When  an  animal  is  supplied  with  known  quantities  of  food  per 
day,  it  is  possible,  by  collecting  the  feces  and  subjecting  it  to  the 
same  chemical  analysis  as  was  applied  to  the  food,  to  determine 
how  much  of  each  constituent  of  the  food  has  been  digested  by 
the  animal.  This  applies  particularly  to  carbohydrates,  fats  and 
proteins,  although  not  strictly  accurate  for  these.  It  does  not 
apply  to  the  mineral  salts,  as  they  are  partly  excreted  through 
the  intestine.  But  by  such  means  the  digestibility  of  feeds  is 
measured  and  such  results  are  of  enormous  value  to  the  knowledge 
of  animal  feeding. 


CHAPTER  X 

FEEDING  STANDARDS 

We  have  traced  in  the  preceding  chapter  the  processes  of  solu- 
tion and  the  destination  of  the  various  nutrients  of  feeding  ma- 
terials. It  will  now  be  necessary  to  consider  briefly  the  develop- 
ment of  our  knowledge  leading  to  the  establishment  of  feeding 
standards  and  the  present  status  of  such  information.  In  1810 
Thaer,  in  Germany,  formulated  the  first  standard,  publishing  a 
table  of  hay  equivalents,  using  meadow  hay  as  the  standard.  It 
had  little  experimental  foundation  and  soon  fell  into  disuse.  In 
1859  Grouven  published  the  first  standard  based  upon  the  quan- 
tity of  proximate  constituents  in  feeding  materials. 

The  work  of  Liebig,  Boussingault,  and  others,  with  the  new 
tools  of  a  rapidly  developing  chemistry,  was  paving  the  way  for 
standards  based  on  chemical  analysis.  But  the  tables  of  Grouven 
did  not  meet  the  requirements,  since  they  were  based  on  the  total, 
instead  of  the  digestible  nutrients. 

In  1864  the  feeding  standards  of  Wolff,  the  eminent  German 
scientist,  first  appeared.  They  are  based  upon  the  amounts  of 
digestible  protein,  carbohydrates  and  fats,  required  by  the  vari- 
ous classes  of  farm  animals.  These  standards  have  been  pub- 
lished annually  in  the  Mentzel-Lengerke  calendar  down  to  1896 ; 
for  the  next  ten  years  they  were  issued  by  Lehmann  of  the  Berlin 
Agricultural  High  School,  and  since  1907  by  Kellner,  modified 
to  a  starch  equivalent  basis,  to  be  described  later.  The  Wolff 
standards  have  seen  wide  use  by  practical  stockmen  because  of 
their  simplicity  and  definiteness. 

Co-efficient  of  digestibility.  The  nutrients  of  feeds  are  not 
wholly  digestible.  A  part  passes  through  the  animal  without 
having  been  dissolved  by  the  digestive  juices  and  thereby  made 
available  to  the  animal.  The  general  method  of  measuring  the 
digestibility  of  feeds  has  been  to  supply  the  animal  with  weighed 
quantities  of  the  feed,  the  composition  of  which  has  been  deter- 


240 


'Agricultural  Chemistry 


mined  by  chemical  analysis.     During  the  experiment  the  solid 
excrement  is  collected  and  weighed  and  finally  analyzed  by  the 
same  methods  as  those  previously  applied  to  the  feed.     From  the 
data  thus  collected  the  digestion  co-efficients  are  calculated. 
Example : 

Digestion  Experiment  with  Sheep  (From  Henry) 


Nitro- 

Dry 

Crude 

Crude 

gen 

Ether 

Matter 

Protein 

fiber 

free 

extract 

extract 

Grams 

Grams 

Grams 

Grams 

Grams 

Fed  700  grams  of  hay   (con- 

taining)   

586.1 

77.7 

191.5 

276.7 

10  7 

Excreted    610.6    grains    dung 

(containing)  

288.6 

40.4 

101.5 

119.4 

7  9 

Digested  

297.5 

37.3 

90.0 

157.3 

2  8 

Per  cent  digested  

50  8 

48.0 

47.1 

56  8 

26  2 

From  the  example  it  will  be  seen  that  the  digestion  co-efficient 
is  the  proportion  of  each  food  constituent  digested  out  of  100 
parts  by  weight  supplied.  The  figures  secured  are  not  absolutely 
accurate,  due  to  intestinal  secretions  which  become  reckoned  as 
undigested  food.  The  co-efficients  for  proteins  and  fats  suffer 
most  in  this  regard.  In  experiments  with  oat  straw  the  fecal  ni- 
trogen has  been,  found  to  be  more  than  that  in  the  food,  although 
the  protein  of  the  straw  must  have  been  digested  to  a  considerable 
extent.  Jordan  states:  "It  is  probably  safe  to  affirm  that  at 
least  10  should  be  added  to  the  co-efficients  of  digestibility  of  the 
protein  of  coarse  fodders,  as  usually  given  in  the  tables  that  have 
been  compiled."  With  fat  co-efficients,  an  error  is  introduced 
through  the  secretion  of  bile  into  the  intestine.  This  material 
contains  products  soluble  in  ether,  the  usual  reagent  used  in  de- 
termining the  fat  content  of  the  feeding  stuff.  Consequently  the 
undigested  fat  appears  larger  than  it  really  is. 


Feeding  Standards  241 

Conditions  affecting  digestibility.  Animals  differ  in  their 
power  of  digesting  any  given  food  or  food  constituent.  For  ex- 
ample, the  ruminants,  by  their  more  thorough  and  repeated  mas- 
tication, are  better  able  to  digest  bulky  fodder  than  are  pigs  and 
horses.  This  is  illustrated  in  the  following  table  taken  from 
Jordan : — 

Dry  Substance  Digested  from  Meadow  Hay  (Per  cent) 

Samples        Best        Medium        Poor 

Sheep    42  67  61  55 

Oxen    10  67  64  56 

Horses  18  58  50  46 

On  the  other  hand  the  power  of  digesting  bulky  feeds  by  dif- 
ferent classes  of  ruminants  is  very  similar.  Steers  have  been 
compared  with  sheep,  and  cows  with  goats,  with  no  uniform  dif- 
ference in  their  digestive  power  for  this  class  of  feeds. 

With  the  grains,  the  differences  in  digestibility  with  the  various 
classes  of  farm  animals  are  not  greatly  unlike.  Comparative 
trials  of  oats  with  sheep  and  the  horse  gave  nearly  identical  di- 
gestibility of  the  dry  matter.  With  cows  the  result  was  similar. 
In  other  trials  where  beans  were  used  the  advantage  was  slightly 
with  the  ruminant.  Swine  digest  the  concentrated  feeds  as  com- 
pletely as  do  ruminants  or  the  horse.  Nor  are  they  incapable  of 
digesting  vegetable  fiber  when  presented  in  a  favorable  condi- 
tion. Pigs  fed  on  green  oats  and  vetch  digested  48.9  per  cent  of 
the  fiber  supplied.  However,  the  digestive  apparatus  of  the  pig 
is  not  adapted  for  dealing  successfully  with  bulky  fodder. 

So  far  as  the  influence  of  breed  is  concerned,  this  does  not  be- 
come a  factor  in  the  digestibility  of  feeds.  A  Jersey  is  as  ef- 
ficient in  this  capacity  as  a  Holstein.  Young  animals  appear  to 
digest  as  efficiently  as  older  ones  of  the  same  species.  There  are, 
very  probably,  differences  in  individuals,  but  the  data  so  far  col- 
lected do  not  definitely  show  this. 

The  influence  of  quantity  of  food  on  digestion  is  an  unsettled 
point.  The  old  experiments  of  Wolff  indicated  that  a  full  ration 
was  as  completely  digested  as  a  scanty  one.  More  recent  experi- 


242  Agricultural  Chemistry 

ments  in  Europe,  as  well  as  in  this  country,  give  opposite  results, 
indicating  a  higher  rate  of  digestibility  with  smaller  rations.  The 
difference  is  not  large  and  with  appetite  regulating  the  consump- 
tion, it  is  fair  to  assume  that  variations  in  food  intake,  incidental 
to  normal  feeding,  will  not  markedly  influence  the  power  of  di- 
gestion. 

Influence  of  the  quality  of  feed  on  digestibility.  It  is  a  popu- 
lar belief  that  curing  a  fodder  decreases  its  digestibility.  This  is 
probably  true,  especially  where  the  drying  has  been  conducted 
in  a  careless  manner.  The  loss  of  leaves  and  the  finer  parts  of 
the  plant,  and  the  washing  out  of  soluble  matter  by  rain  are 
factors  which  will  depress  the  digestibility  of  the  fodder.  For 
this  reason,  field  cured  corn  fodder  is  considerably  less  digestible 
than  silage  coming  from  the  same  source.  On  the  other  hand, 
where  the  curing  is  done  in  such  a  manner  as  to  exclude  these 
losses,  it  is  doubtful  if  it,  in  itself,  has  any  appreciable  effect 
upon  digestibility. 

The  stage  of  growth  of  a,  fodder  plant  will  influence  its  digesti- 
bility. That  stage  where  there  is  a  relatively  high  proportion  of 
starch  and  sugar  and  a  minimum  of  cellulose  and  lignins,  will 
show  a  higher  digestibility.  As  the  grasses  mature,  the  fiber  in- 
creases; on  the  other  hand,  the  corn  plant  furnishes  a  relatively 
higher  proportion  of  digestible  nutrients  when  the  ears  are  full 
grown  than  before  the  ears  have  formed. 

Influence  of  methods  of  preparation.  Steaming,  wetting  and 
cooking  the  feed  have  received  considerable  attention.  The  gen- 
eral concensus  of  opinion  of  feeders,  as  well  as  the  results  of 
scientific  experiments,  do  not  indicate  that  these  practices  are  of 
great  advantage;  beans,  corn  and  bran  are  not  better  digested  by 
the  horse  or  ox  when  previously  soaked  in  water.  Barley,  corn 
and  pea  meal  have  been  found  more  nourishing  for  pigs  when 
given  dry  than  when  previously  cooked.  Cooking  certainly  de- 
presses the  digestibility  of  the  proteins.  This  has  been  experi- 
mentally demonstrated  with  steamed  hays,  silage,  corn  meal  and 
wheat  bran.  However,  when  cooking  or  steaming  the  feed  ren- 


Feeding  Standards  243 

ders  it  more  palatable,  and  secures  a  larger  consumption  of  ma- 
terial which  otherwise  would  be  wasted,  the  influence  on  digesti- 
bility is  of  less  importance. 

Grinding  increases  the  digestibility  of  feeds.  Mechanical  di- 
vision is  an  important  factor  in  the  rate  and  completeness  of  solu- 
tion of  material  in  the  digestive  tract.  A  single  experiment  with 
corn,  fed  to  the  horse,  showed  about  7  per  cent  increased  digesti- 
bility from  grinding,  and  with  wheat,  in  one  trial  the  increase 
was  10  per  cent.  With  ruminants  the  danger  from  imperfect 
mastication  is  less  than  with  horses  and  swine.  W}iether  it  will 
pay  to  grind  the  grain  will  depend  upon  the  cost  of  grinding  and 
the  loss  of  nutritive  material  from  not  grinding. 

Influence  of  one  feed  on  the  digestibility  of  another.  It  is 
generally  stated  that  the  addition  of  a  considerable  quantity  of 
protein  to  a  ration  of  hay  and  straw  consumed  by  a  ruminant, 
is  completely  digested,  without  affecting  the  digestibility  of  the 
original  feed.  Pigs  have  been  fed  potatoes  to  which  variable 
quantities  of  meat  flour  were  added.  The  proteins  of  the  meat 
were  completely  digested,  while  the  proportion  of  potatoes  di- 
gested remained  unchanged. 

It  is  also  claimed  that  the  addition  of  fat  or  oil  to  a  basal  ration 
of  hay  and  straw  was  without  influence  on  their  digestibility. 

On  the  contrary,  Dietrich  and  Koenig  state  that  if  a  carbohy- 
drate, as  starch  or  sugar,  is  added  to  the  extent  of  more  than  10 
per  cent  of  the  dry  substance  of  a  basal  ration,  or  if  roots  or 
potatoes,  equivalent  in  dry  matter  to  more  than  15  per  cent,  are 
fed,  a  diminution  of  digestibility  occurs.  It  is  further  stated 
that  the  depression  of  digestibility  is  reduced,  when,  accompany- 
ing the  high  starch  intake,  there  is  a  corresponding  increase  in 
protein  consumption.  From  these  considerations,  it  is  stated 
that  highly  nitrogenous  feeds  may  be  given  with  hay  and  straw 
without  affecting  their  digestibility;  but  feeds  rich  in  carbohy- 
drates, as  potatoes  and  mangels,  cannot  be  given  in  greater  pro- 
portion than  15  per  cent  of  the  fodder  (both  calculated  as  dry 
food)  without  diminishing  the  digestibility  of  the  latter. 


244  Agricultural  Chemistry 

Lindsey  of  the  Massachusetts  Station  has,  in  part,  confirmed 
the  work  of  Dietrich  and  Koenig.  He  found  that  when  Porto 
Eico  molasses  fed  together  with  hay,  constituted  from  10  to  15 
per  cent  of  the  total  dry  matter  of  the  ration,  little  if  any  de- 
pression occurred.  But  with  molasses  constituting  20  per  cent 
of  the  dry  matter  of  the  ration,  a  depression  of  4.5  per  cent  was 
noted  in  the  digestibility  of  the  hay.  He  concluded.that  molasses 
and  hay  would  not  make  a  satisfactory  combination  for  farm 
stock.  A  more  suitable  ration  would  consist  of  hay,  together 
with  one  or  more  protein  concentrate  and  molasses.  Even  in  a 
ration  of  hay  and  gluten  feed  and  in  which  molasses  composed 
20  per  cent  of  the  dry  matter,  there  was  a  depression  of  8  per 
cent  in  the  digestibility  of  the  hay  and  gluten. 

The  nutritive  ratio.  We  have  seen  that  the  formulation  of 
feeding  standards  must  be  based  on  a  knowledge  of  the  relative 
digestibility  of  the  several  nutrients  contained  in  the  feeding 
material.  Such  knowledge  has  been  secured  by  many  experi- 
menters, working  with  various  classes  of  farm  animals,  and  has 
given  us  our  tables  of  co-efficients  of  digestibility  available  in 
books  on  animal  feeding.  (See  table  in  Appendix.) 

It  has  been  found  in  practice  that  the  feed  of  an  animal  may 
be  varied  within  fairly  wide  limits,  provided  the  ratio  of  digesti- 
ble protein  to  all  other  digestible  organic  matter  is  kept  within 
certain  limits.  Protein  has  special  and  peculiar  functions  and 
less  than  a  certain  minimum  would  limit  production  ~by  just  the 
amount  of  the  deficiency.  In  order  to  get  this  ratio  it  is  neces- 
sary that  some  carbohydrate  be  taken  as  a  standard  for  express- 
ing the  non-protein  portion  of  the  ration.  Starch  is  the  sub- 
stance always  chosen,  and  it  becomes  necessary,  in  order  to  express 
the  fats  and  other  carbohydrates  in  terms  of  starch,  to  obtain 
the  equivalent  in  heat  producing  power  of  the  other  food  con- 
stituents. This  has  been  secured  (1)  by  burning  a  weighed 
portion  of  the  various  materials  in  a  calorimeter  (an  instrument 
for  measuring  heat  production),  and  (2)  by  direct  experiments 
upon  animals  placed  in  a-  respiration  calorimeter  (an  apparatus 


Feeding  Standards  245 

for  measuring  both  gas  and  heat  production),  and  fed  with  known 
weights  of  the  various  feeding-stuffs.  As  an  average  of  several 
experiments  it  may  be  taken  that  one  part  of  fat  evolves  as  much 
heat  as  2.4  parts  of  starch,  sugar,  cellulose  or  of  protein.  To 
express  the  non-protein,  other  than  carbohydrates,  in  terms  of 
starch  it  is  therefore  necessary  to  multiply  the  quantity  of  di- 
gestible fat  by  2.4  and  add  this  product  to  the  quantity  of  digest- 
ible carbohydrates  present.  The  nutritive  ratio  thus  becomes : 

digestible  protein 


digestible  carb.  -f   (dig.  fat  X   2.4) 

The  nutritive  ratio  of  corn  meal  is  obtained  as  follows : 

100  Ibs.  contain  7.9  Ibs.  digestible  protein 

66.7  Ibs.  digestible  carbohydrates 
4.3  Ibs.  digestible  ether  extract  (fat) 

7.9  7.9  7.9  1 


60.7  +  (  4.3  X  2.4  )  06.7  +  9.32  76.02  9.6 

The  nutritive  ratio  for  corn  meal  is  therefore  1:9.6.  This 
means  that  for  every  pound  of  digestible  protein  in  corn  meal 
there  are  9.6  pounds  of  digestible  carbohydrates  and  ether  ex- 
tract (fat)  equivalent.  The  term  wide  ratio  is  used  when  there 
is  a  very  large  proportion  of  carbohydrates  contained  in  a  feed 
in  proportion  to  the  protein.  Oat  straw,  with  a  nutritive  ratio 
of  1:33.7,  is  an  example  of  a  very  "wide"  nutritive  ratio.  With 
corn  the  ratio  is  medium,  while  with  oil  meal,  with  a  ratio  of 
1 :1.7  the  expression  narrow  is  used. 

The  Wolff-Lehman  feeding  standards.  In  1864  Wolff  pro- 
posed certain  feeding  standards,  which  have  been  largely  used  in 
framing  rations.  In  order  to  eliminate  the  size  of  the  animal, 
the  proportion  of  the  various  feed  constituents,  to  be  supplied 
daily  for  1000  pounds  of  body  weight,  are  given.  For  illustra- 
tion, a  few  standards  are  given  here.  (See  full  table  in  Ap- 
pendix.) 


246 


Agricultural  Chemistry 
For  1000  Pounds  Live  Weight  Daily 


Digestible 

Dry 

Nu- 

Sub- 

tritive 

stance 

Protein 

Carbo- 
hydrates 

Fat 

Ratio 

Lbs. 

Lbs. 

Lbs. 

Lbs. 

Cow,  inilk  yield  22  Ibs  

29 

2.5 

13 

0.5 

1:5.7 

Fattening  steer,  1st  period  .  . 
Horse,  medium  work  

30 
24 

2.5 
2.0 

15 
11 

0.5 
0.6 

1:6.5 
1:6.2 

In  formulating  standards  for  ruminants  it  is  better  to  start 
with  two  kinds  of  roughage,  furnishing  from  16  to  20  pounds  of 
dry  matter,  and  about  10  pounds  of  carbohydrates  (nitrogen 
free-extract),  and  then  add  concentrates,  which  will  on  first  cal- 
culation bring  the  total  digestible  protein  somewhat  under  the 
standard.  The  additional  requirements  can  then  be  easily  com- 
puted. The  term  "fat"  is  identical  with  the  "ether  extract." 

It  is  not  necessary  that  a  ration  agree  mathematically  in  all 
nutrients  with  the  standard.  To  attempt  to  do  this  is  to  avoid 
the  individual  possibilities  of  the  animal.  The  tables  of  digestion 
co-efficients  and  feeding  standards  are  but  averages  and  approx- 
imations. They  are  not  to  be  followed  blindly  and  absolutely, 
but  if  taken  as  guides,  they  can  become  extremely  helpful.  For 
example,  the  Wolff  standards  are  quantities  to  be  fed  per  thou- 
sand pounds  of  live  weight.  It  is  known  that  the  food  demands 
of  an  organism  are  not  proportional  to  its  size,  but  rather  to  its 
surface.  This  is  because  of  a  difference  in  demand  on  the  heat 
producing  function  of  a  food.  A  small  animal  has  a  propor- 
tionately greater  surface  to  its  weight  than  a  larger  animal.  Con- 
sequently it  does  not  require  the  same  proportional  amount  of 
digestible  food  to  maintain  a  1700  pound  steer  as  one  weighing 
1000  pounds.  For  instance,  Kuhn  of  the  Mockern  Station,  found 
that  a  1900  pound  ox  could  be  maintained  on  0.7  pound  of  di- 
gestible protein  and  6.6  pounds  of  digestible  carbohydrates. 
Other  investigators  have  found  that  the  Wolff  allowances  may  be 
too  high.  Haecker  of  the  Minnesota  Station  maintained  a  dry, 


Feeding  Standards 


247 


barren  cow  of  a  1000  pounds  weight  on  0.6  pound  of  digestible 
protein,  6  pounds  of  digestible  carbohydrates,  and  0.1  pound  of 
digestible  fat  (ether  extract). 

Energy  value  of  feeds.  The  function  of  food,  as  has  already 
been  pointed  out,  is  not  only  to  repair  waste  and  promote  growth 
and  increase,  but  also  to  furnish  heat  and  energy.  For  this  rea- 
son, attempts  have  been  made  by  several  investigators  to  assess 
the  relative  value  of  feeds  by  a  determination  of  their  heat  pro- 
ducing power.  Heat  units  are  expressed  either  in  starch  equiv- 
alents or  calories.  The  German  investigators,  Kellner  and  Zuntz, 
have  used  starch  as  the  basis  for  expression,  while  Armsby  of 
this  country  is  using  the  calorie.  The  calorie  represents  the 
quantity  of  heat  required  to  raise  the  temperature  of  one  gram 
of  water  from  0°  to  1°  C.  A  large  Calorie,  one  thousand  times 
larger  than  the  small  calorie,  is  usually  employed  for  the  ex- 
pression of  large  quantities  of  heat  and  will  be  used  here,  gen- 
erally. However,  the  new  term,  therm,  which  represents  1000 
large  Calories,  is  now  in  use  by  Armsby  and  is  the  quantity  of 
heat  required  to  raise  the  temperature  of  1000  kilograms  of 
Avater  1°  C. 

The  value  in  large  Calories  of  one  gram  of  the  several  classes 
of  nutrients,  is  given  in  the  following  table: 

Wheat  gluten   5.8   Cellulose  4.1 

Animal   muscle    5.7    Cane  sugar 4.0 


Starch  4.1 


Animal   fat   .  .  9.4 


Perhaps  it  would  be  clearer  to  express  the  total  energy  of  some 
of  the  above,  as  well  as  a  few  common  feeding  materials  as  therms 
per  100  pounds. 


Therms 
per  100 
Ibs. 


Therms 

per  100 

Ibs. 


Pure  protein  186 

Pure  carbohydrates 186 

Pure  fat 422 


Timothy  hay  15%  moisture.  .175. 1 

Oat  straw  15%  moisture 171.0 

Corn  meal  15%  moisture 170.9 

Linseed  meal  15£  moisture  . . .  196. 7 


248 


Agricultural  Chemistry 


Available  energy.  The  data  in  the  above  table  are  secured  by 
complete  combustion  of  the  material  in  the  calorimeter.  Such 
does  not  obtain  in  the  animal  body.  It  sKbuld  be  remembered 
that  only  part  is  digested,  and  as  only  the  digested  portion  fur- 
nishes available  energy,  the  available  fuel  value  of  a  ration  must 
depend  primarily  upon  the  amount  which  is  dissolved  out  of  the 
digestive  tract  and  passes  into  the  blood.  There-  is  fuel  waste  in 
the  solid  excrement  of  the  feces,  in  the  incompletely  burned  gases 
escaping  from  the  alimentary  canal,  and  in  the  unoxidized  com- 
pounds of  the  urine.  It  has  been  estimated  by  Kuhn  that  the 
loss  of  energy  in  the  gas,  methane,  which  has  its  source  in  the 
fermentations  of  the  digestive  tract,  amounts  to  over  one-seventh 
of  the  energy  of  the  digested  crude  fiber  and  carbohydrates.  In 
the  following  table  are  recorded  such  data  secured  on  oxen.  This 
table  shows  both  the  actual  therm  balance  and  in  addition  the 
percentage  distribution  of  the  therms. 

Available  Energy  in  100  Pounds 


Total 

In  gas 

Avail- 

energy 

Fecee    '< 

Urine 

methane 

Loss 

able 

therms 

therms 

therms 

therms 

therms 

therms 

Corn  rueal  

170.9 

15.7 

6.6 

15.9 

38.2 

132.7 

Timothy  hay  .  . 

179.3 

87.7 

5.5 

6.8 

100.0 

79.3 

Wheat  straw  .  .  . 

171.4 

93.9 

4.3 

15.5 

113.7 

57.7 

Per  cent 

Corn  meal  

100 

9.2 

3.9 

9.3 

22.4 

77.6 

Timothy  hay  .  . 

100 

48.9 

3.1 

3.8 

55.8 

44.2 

Wheat  straw.  .  . 

100 

54.9 

2.5 

9.0 

66.3 

33.7 

From  this  we  see  that  the  available  energy  of  a  ration  represents 
the  fuel  value  of  the  dry  matter  digested  from  it,  minus  the 
energy  in  the  dry  matter  of  the  urine  and  that  lost  in  excreted 
gases.  Such  data  have  been  secured  on  a  number  of  materials 
by  the  use  of  the  respiration  apparatus — an  air  tight  compart- 
ment in  which  the  animal  could  live  and  from  which  the  gases 


Feeding  Standards  249 

could  be  removed  for  analysis.  At  the  same  time  the  urine  and 
feces  could  also  be  collected  for  a  complete  chemical  analysis  and 
for  a  determination  of  the  energy  still  contained  in  them. 

Net  available  energy.  We  have  seen  that  food  is  not  applied 
to  use  until  it  reaches  the  blood.  It  must  have  work  done  upon 
it  before  it  is  in  solution.  The  processes  of  mastication,  of  mov- 
ing it  along  the  digestive  tract,  and  of  bringing  it  into  solution 
all  require  the  expenditure  of  a  certain  amount  of  energy.  Zuntz, 
working  with  a  horse,  has  attempted  to  measure  this.  His  method 
has  been  to  determine  by  various  devices,  how  much  more  oxygen 
is  consumed  during  mastication  and  digestion  than  before  or 
after  these  operations  are  accomplished.  From  this  measure  of 
oxygen  consumption,  he  calculated  the  following  heat  units,  rep- 
resenting the  energy  used  in  chewing  certain  feeds: 

Cal. 

1  pound  corn   (454  grams)    6.3 

1  pound  oats   21.0 

1  pound  hay   76.0 

This  is  an  important  finding.  Zuntz  calculates  that  in  general 
the  coarse  feeds  have  20  per  cent  less  net  energy  value  than  the 
grains  and  that  the  work  of  mastication  and  digestion  combined 
is  about  48  per  cent  of  the  energy  value  of  the  digested  material 
from  hay  and  19.7  per  cent  of  that  from  oats.  We  must  remem- 
ber, however,  that  the  wastefulness  of  fibrous  foods  shown  in 
these  determinations  on  the  horse  are  not  true  to  an  equal  extent 
in  the  case  of  ruminants.  In  the  latter  the  fiber  is  softened  in  the 
paunch  and  its  digestion  has  begun  before  it  reaches  the  intestines. 

Net  available  energy  then,  is  the  available  energy  minus  the 
energy  of  digestion  and  preparation  of  the  food  for  use.  This 
internal  work  furnishes  heat,  and  provided  it  is  not  in  excess  of 
the  heat  requirement  of  the  animal,  should  not  be  regarded  as 
waste.  The  waste  of  heat  has  begun  when  that  produced  by  the 
work  of  digestion  exceeds  the  animal  requirement.  But  if  it  is 
produced  in  the  digestive  tract  and  not  in  the  tissues  of  the  ani- 
mal, it  cannot  appear  as  useful  work. 


250 


Agricultural  Chemistry 


From  the  work  of  Zuntz,  Kellner  at  the  Mockern  Station  and 
Armsby  in  this  country,  measurements  of  the  net  available  en- 
ergy of  some  feeds  have  been  made  or  methods  developed  for 
their  calculation.  In  the  table  that  follows  the  consumption  of 
energy  in  the  process  of  food  digestion,  blood  circulation  and 
tissue  storage  is  recorded  for  a  few  feeds  and  the  net  energy  ex- 
pressed in  therms  and  also  as  per  cent  of  the  total  energy  of  the 
feed. 

Net  Available  Energy  100  Ws.  Feed 


Total 
therms 

Available 
therms 

Used  in  prod, 
processes 
therms 

Net 
avail, 
therms 

Net 
avail.  % 
of  total 

Corn  meal  

170.9 

132.7 

62.0 

70.7 

41.3 

Timothy  hay  
Wheat  straw  

179.3 
171.4 

79.3 
57.7 

52.9 
47.4 

26.4 
10.3 

14.7 
6.0 

We  learn  from  this  that  it  is  not  the  total  chemical  energy  in 
a  feeding  stuff  which  measures  its  value  to  the  body,  but  that 
which  remains  after  deducting  the  energy  losses  in  the  unburned 
material  of  the  excreta,  the  energy  expended  in  digesting  the  real 
fuel  materials  from  the  food,  and  in  addition,  the  energy  used  in 
transforming  them  into  substances  which  the  body  can  use  or 
store  up.  This  gives  us  what  Kellner  calls  the  production  value 
of  feeds,  and  is  identical  in  meaning  with  the  term  net  available 
energy  of  feeds. 

Production  value  of  feeds.  From  elaborate  experiments  with 
the  respiration  chamber  and  mature  oxen  Kellner  has  determined 
the  production  value  of  certain  feeds.  For  this  purpose  he  chose 
rather  lean  oxen,  giving  them  a  fixed  moderate  ration  which  re- 
sulted in  a  small  increase  in  weight.  He  then  added  to  the  ration 
the  feed  to  be  experimented  with,  and  determined  the  amount  of 
increase  produced.  This  was  not  done  by  weighing  the  animal, 
but  by  determining  the  amount  of  nitrogen  and  carbon  retained 


Feeding  Standards 


251 


by  the  animal.  The  protein  tissue  stored,  was  calculated  from 
the  nitrogen  retained  and  the  fat  from  the  carbon  left  after  de- 
ducting the  carbon  required  to  build  the  increase  in  protein. 
Kellner's  results  are  shown  in  the  following  table  and  although, 
expressed  differently  are  in  harmony  with  those  presented  above,, 
but  which  were  expressed  as  therms. 

The  available  energy  of  these  feeds  had  already  been  deter- 
mined and  is  given  in  the  first  column.  In  the  second  column 
appears  the  percentage  of  loss  in  the  process  of  digestion  and 
assimilation  and  production  of  tissue.  The  last  two  columns  ex- 
press the  energy  value  of  the  increase  and  the  comparative  pro- 
duct:on  value  of  the  different  materials,  with  starch  as  a  unit. 
We  see  from  this  that  56.3  per  cent  of  the  digested  fat  (peanut, 
oil)  was  stored,  and  44.7  per  cent  of  the  digested  protein  (wheat 

Heat  Values  of  Digested  Feeds  and  of  the  Increase  Obtained 
in  a  Fattening  Ox 


Heat  value 
to  the  ox  of 
1  gram  of 
digested 
substance 

Loss  of 
ienergy  in 
production 
processes 

Heat  value 
of  increase 
obtained 

Comparative- 
production 
value. 
Starch  100 

Starch  

Cals 
3.7 

Per  cent 
41.1 

Cals. 
2.2 

100 

Molasses  

3.6 

36.4 

2.3 

104 

Straw  pulp  

3.6 

36.9 

2.3 

104 

Wheat  gluten  

4.7 

55.3 

2.1 

101 

Peanut  oil  

8.8 

43.7 

4.9 

224 

Meadow  hav  

3.6 

58.5 

1.5 

68 

Oat  Straw  

3.7 

62.4 

1.4 

64 

Wheat  straw  

3.3 

82.2 

1.6 

27 

gluten),  while  but  17.8  per  cent  of  the  digested  wheat  straw  was 
available  for  useful  energy  or  increase.  This  gives  us  a  scien- 
tific explanation  of  the  fact  that  coarse  feeds  are  not  adapted  to- 
rapid  production. 

From  such  data  Kellner  concludes  that  1  pound  of  digested 


252 


Agricultural  Chemistry 


starch  may  yield  a  maximum  of  0.23  pound  of  body  fat,  the  rest 
being  consumed  in  the  transformation  processes.  Taking  1  pound 
of  digestible  starch  as  his  standard,  he  has  formulated  the  rela- 
tive values  for  the  digestible  nutrients  in  feeding  stuffs,  based  on 
the  amount  of  body  fat  the  several  pure  nutrients  would  form  if 
fed  to  the  ox. 

Kellner's  starch  values.  These  are  the  values  of  the  nutrients 
of  feeds  expressed  with  starch  as  a  unit  of  energy.  From  the 
quantities  of  digestible  nutrients  in  1000  pounds  of  ordinary 
feeding  material,  the  relative  value  of  feeds  for  maintenance  and 
production  in  terms  of  starch  have  been  calculated  by  Kellner. 
No  extended  table  will  be  given  here.  However,  to  make  this 
clear  the  digestible  nutrients  in  a  few  common  feeding  materials 
are  brought  together  in  the  following  table.  This  table  includes 
the  amides,  which  are  not,  in  American  tables  as  a  rule,  dis- 
tinctly separated,  but  included  under  the  term  " crude  protein" 
(NX  6.25). 

Pounds  of  Digestible  Matter  in  1000  Pounds  of  Various  Feeds 


\ 

Total 
organic 
matter 

Nitrogenous  Substances 

Fat 

Carb. 

Fiber 

Protein 

Amides 

Corn  

786 
600 
715 
440 
381 
351 

73 
81 
70 
47 
7 
4 

6 

7 
4 
25 
5 

i 

44 
45 

19 
13 

7 
4 

651 
441 
607 
269 
163 
150 

12 
26 
15 
151 
199 
193 

Oats  

Barlev  

Clover  hay  

Oat  straw  

Wheat  straw  

From  these  data  the  maintenance  value  in  terms  of  starch  is 
made  by  the  simple  calculation  r — Protein  X  1.251  -j-  Amides  X 
0.6  -f  Fat  X  2.3  +  Carb.  +  Fiber. 


i  The  factors  1.25,  0.6,  and  2.3  are  those  in  use  in  Europe  for  convert- 
ing the  food  constituents  to  an  energy  basis  equivalent  to  starch.  It 
should  be  observed  that  generally  the  factor  2.4  for  fat  is  the  only  one 
used. 


Feeding  Standards 


253 


From  this  we  see  that  the  feeds  for  maintenance  are  valued  at 
the  full  heat  value  of  the  digestible  constituents.  The  heat  which 
is  the  final  outcome  of  the  mechanical  labor  employed  in  diges- 
tion, can  serve  for  warming  the  animal.  But  when  the  produc- 
tion value  is  considered,  it  has  been  found  that  if  we  take  only 
the  digestible  fat,  protein,  and  carbohydrates  of  the  ration,  and 
give  to  each  the  energy  value  found  for  it  in  Kellner's  production 
experiments,  the  sum  of  these  will  approximate  the  values  actu- 
ally obtained  in  the  experiments  tried.  Consequently  the  pro- 
duction value  in  terms  of  starch  =  Fat  X  2.3  -j-  Protein  -f-  Garb. 

In  the  following  table  are  assembled  a  few  examples  of  the 
starch  equivalents  of  feeds  for  both  maintenance  and  production  f 
as  formulated  by  Kellner. 

Comparative  Value  of  Ordinary  Feeds  for  Oxen  and  Sheep 


For  Maintenance 

For  Production 

Value  of 
1000  Ibs.  as 
starch 

Quantities 
equivalent 
to  1  Ib.  of 
starch 

Value  of 
1000  Ibs.  as 
starch 

Quantities 
equivalent 
to  1  Ib.  of 
starch 

Corn   

859 
676 
755 
459 
412 
357 

1.16 

1.48 
1.32 
2.18 
2.43 
2.80 

825 
626 
721 
319 
207 
96 

1.21 
1.60 
1.39 
3.13 
4.83 
10.41 

Oats  

Barley  

Clover  ha  v  

Oat  straw  

Wheat  straw  

Kellner  admits  that  our  knowledge  of  the  actual  production 
value  of  feeds  is  still  very  incomplete.  Such  values  have  been 
determined  by  actual  experiments  in  only  a  few  cases  and  then 
only  for  the  mature  fattening  ox.  It  serves,  however,  to  illus- 
trate the  trend  of  experimentation  and  the  serious  and  laborious 
attempts  being  made  to  place  the  nutritive  value  of  feeding  stuffs 
on  a  scientific  experimental  basis.  It  appears  from  the  above 
table  that  approximately  2  pounds  of  oat  or  wheat  straw  may 


254 


Agricultural  Chemistry 


replace  1  pound  of  corn,  if  the  ox  or  sheep  is  merely  on  a  main- 
tenance diet,  but  that  1  pound  of  corn  will  have  as  great  an  ef- 
fect as  4  pounds  of  oat  straw  or  10  pounds  of  wheat  straw  when 
the  animal  must  grow  or  fatten. 

Kellner's  feeding  standards.     The  table  on  this  page  is  a  brief 
summary  of  these  standards. 

Standard  Rations  for  1000  Lbs.  of  Farm  Animals 


Dry 

matter 

Digestible  Nutrients 

Proteins 

Starch  value 

Maintenance  of  mature  steers  

Lbs. 
15-21 
24-32 
25-29 
27-33 
18-25 
23-29 
33-37 
28-33 
24-28 

Lbs. 
0.6 
1.5-1.7 
1.6-1.9 
2.2-2.5 
1.0 
2.0 
3.0 
2.8 
2.0 

Lbs. 

6.0 
12.5-14.5 
9.8-11.2 
11.8-13.9 
9.2 
15.0 
27.5 
26.1 
19.8 

Fattening  steers  .  .   . 

Milch  cow  giving  20  Ibs.  milk  daily  .  .  . 
Milch  cow  giving  30  Ibs.  milk  daily  .  .  . 
Horse  at  light  work  

Horse  at  heavy  work  

Fattening  swine  1st  period  

fattening  swine  2nd  period  

Fattening  swine  3rd  period  

Armsby's  feeding  standards.  As  an  outgrowth  of  the  work 
of  Kellner  and  continued  work  with  the  respiration  calorimeter, 
Armsby  has  begun  to  formulate  feeding  standards,  giving  the  net 
production  energy  of  feeding  stuffs.  These  are  expressed  in 
therms,  and  for  illustration  several  examples  are  brought  together 
in  the  first  table  on  page  255.  The  complete  table  will  be  found 
in  the  appendix. 

The  table  is  supposed  to  represent,  with  a  fair  degree  of  ac- 
curacy, the  digestible  protein  and  the  net  energy  which  the  vari- 
ous feeding  stuffs  will  supply.  They  express  what  is  available  to 
the  animal  for  growth,  fattening,  work  or  milk  production,  after 
deducting  that  used  in  the  work  of  mastication  and  assimilation. 
The  digestible  protein  in  the  table  is  true  protein  and  does  not 
include  the  so-called  "amides"  of  the  "crude  protein." 


Feeding  Standards  255 

Dry  Matter,  Digestible  Protein  and  Energy  Value  in  100  Lbs. 


Feeding  stuff 

Total 
dry  matter 

Digestible 
protein 

Energy  value 

Green  alfalfa  

Lbs. 
28.2 

Lbs. 
2.50 

Therms 
12.45 

Dry  alfalfa  

91.6 

6.93 

34.41 

Oat  straw  

90.8 

1.09 

21.21 

Corn  meal  

89.1 

6.79 

88.84 

Wheat  bran  

88.1 

10.21 

48.23 

Standards  for  maintenance.  The  following  table  shows  the 
amount  of  digestible  protein  and  net  energy  required  per  head 
for  the  maintenance  of  cattle,  sheep  and  horses  of  different 
weights.  No  figures  for  swine  are  available. 

Armsby's  Maintenance  Standards  for  Horses,  Cattle  and  Sheep 


-r    •__ 

Horses 

Cattle 

Sheep 

Live 
weight 

Digest- 
ible 
protein 

Energy- 
value 

Digest- 
ible 
protein 

Energy 
value 

Live 
weight 

Digest- 
ible 
protein 

Energy 
value 

Lbs. 

Lbs. 

Therms 

Lbs. 

Therms 

Lbs. 

Lbs. 

Therms 

150 

.15 

1.70 

.30 

2.00 

20 

.02 

.30 

250 

.20 

2.40 

.40 

2.80 

40 

.05 

.54 

500 

.30 

3.80 

.60 

4.40 

60 

.07 

'  .71 

750 

.40 

4.95 

.80 

5.80 

80 

.09 

.87 

1000 

.50 

6.00 

1.00 

7.00 

100 

.10 

1.00 

1250 

.60 

7.00 

1.20 

8.15 

120 

.11 

1.13 

1500 

.65 

7.90 

1.30 

9.20 

140 

.13 

1.25 

From  the  table  one  sees  that  a  colt  of  500  Ibs.  weight  will  re- 
quire for  daily  support  0.3  Ib.  of  digestible  protein  and  3.8 
therms,  while  when  it  has  trebled  its  weight  the  requirements  are 
0.65  Ib.  of  digestible  protein  and  7.9  therms.  In  other  words  the 
requirements  have  not  increased  in  proportion  to  the  gain  in 
weight. 


256 


Agricultural  Chemistry 


Standards  for  growing  animals.  The  following  table  gives 
the  digestible  protein  and  energy  required  for  growing  cattle  and 
sheep,  as  set  forth  by  Armsby.  No  data  for  horses  and  swine  are 
available.  The  table  includes  the  maintenance  requirement. 

The  table  shows  that  a  six  months  old  calf,  weighing  425  pounds 
requires  1.3  pounds  of  digestible  protein  and  6  therms  of  energy 
value,  which  includes  the  1.3  pounds  of  protein.  Where  the  calf 
has  grown  to  weigh  1100  pounds,  or  more  than  doubled  its  weight, 
it  requires  0.35  pound  more  protein  and  2  more  therms.  This 
relative  lessening  in  feed  required  is  due  to  the  fact  that  a  larger 
animal  requires  relatively  less  for  maintenance,  and  to  the  addi- 
tional fact  that  the  rate  of  growth  has  greatly  decreased.  Armsby 
allows  1.75  pounds  of  digestible  protein  for  a  steer  weighing 
1000  pounds,  while  but  1.65  is  required  when  the  same  steer 
reaches  1100  pounds.  This  is  due  to  the  lessened  increase  in 
Armsby's  Standards  for  Growing  Cattle  and  Sheep 


Cattle 

Sheep 

Age 

Live 
weight 

Digest- 
ible 
protein 

Energy 
value 

Live 
weight 

Digest- 
ible 
protein 

Energy 
value 

Months 
3  

Lbs. 
275 

Lbs. 
1.10 

Therms 
5.0 

Lbs. 

Lbs. 

Therms 

6  

425 

1  30 

6.0 

70 

.30 

1.30 

9  

90 

.25 

1.40 

12  

650 

1.65 

7.0 

110 

.23 

1.40 

15  

130 

.23 

1.50 

18  

860 

1.70 

7.5 

145 

.22 

1.60 

24  

1000 

1.75 

8.0 

30  

1100 

1.65 

8.0 

muscular  tissue  and  consequently  decreased  demand  for  protein 
food,  as  compared  with  the  earlier  stages  of  life.  It  should  be 
noted  that  in  comparing  maintenance  and  growing  requirements, 
the  larger  part  of  all  the  food  consumed  is  used  for  body  support, 
and  that  additional  requirements  for  growth  are  mainly  in  pro- 
tein, rather  than  therm  requirements. 


Feeding  Standards 


257 


Standards  for  milch  cows  and  fattening  steers.  In  addition 
to  the  foregoing  standards,  Armsby  recommends  the  following : 

1.  For  milk  production  add  to  the  maintenance  standard  0.05 
pound  of  digestible  protein  and  0.3  therm  for  each  pound  of 
average  milk  containing  13  per. cent  of  total  solids  and  4  pec  cent 
of  fat. 

2.  For  fairly  mature  fattening  cattle  add  3.5  therms  to  the 
maintenance  standard  for  each  pound  of  gain  in  live  weight. 

Armsby  does  not  provide  additional  protein  to  the  maintenance 
standard  for  fattening  steers,  holding  that  if  the  proper  allow- 
ance of  therms  is  provided  in  addition  to  the  maintenance  ration, 
no  additional  protein  is  required  for  fattening  purposes.  On  the 
other  hand,  for  milk  production  the  standard  provides  additional 
protein.  This  must  be  done  because  of  the  protein  content  of 
the  milk  itself  and  the  additional  factor  of  protein  supply  for  the 
developing  foetus. 

3.  Armsby  recommends  that  a  1000  pound  ruminant  should 
be  given  from  20  to  30  pounds  of  dry  matter  per  day,  while  for 
the  horse  smaller  amounts  can  be  used. 

Standard  for  the  working  animal.  The  horse  is  the  only  ani- 
mal to  be  considered  here.  "What  applies  to  the  horse  may  also 
be  used  for  the  mule.  As  a  general  average,  Kellner  recommends 
the  following  ration  for  a  1000  pound  horse,  the  amounts  stated 
including  the  maintenance  requirement: — 


Requirements  of  the  Working  Horse 


Digestible  protein 

Energy  value 

For  light  work  

Lbs. 
1.0 

Therms 
9.80 

For  medium  work  

1.4 

12.40 

For  heavy  work  

2.0 

16.00 

258  Agricultural  Chemistry 

Future  of  standards.  The  feeding  standards  being  developed 
at  the  present  time  are  in  a  formative  stage,  and  necessarily  in- 
complete. No  standard  should  be  used  as  an  exact  mathematical 
expression  of  the  animal's  needs.  In  fact  it  cannot  be  done,  be- 
cause we  are  not  in  a  position  to  know  the  exact  requirements  of 
the  individual  animal ;  again,  feeding  stuffs  of  the  same  name 
show  a  considerable  range  in  composition.  Further,  probably  the 
most  important  factor  in  limiting  the  adoption  of  a  feeding 
standard  as  a  final  recipe  in  feeding,  is  the  difference  in  nutritive 
value  and  physiological  action  of  the  nutrients  from  various 
sources.  One  species  of  farm  animal  may  do  better  on  the  nu- 
trients from  one  specific  source,  as  compared  with  those  derived 
from  another.  In  addition,  the  relative  amounts  and  kinds  of 
ash  must  be  considered.  The  value  of  wheat  bran  does  not  re- 
side wholly  in  its  protein  content,  but  partly  in  its  laxative  prop- 
erties, which  are  due  to  a  specific  constituent,  known  as  phytin. 
The  superior  value  of  legume  hays  must  be  attributed,  in  part,  to 
their  high  lime  and  basic  ash  content.  This  is  particularly  true 
when  used  for  growing  animals  and  milch  cows.  All  these  are 
factors  to  be  reckoned  with,  but  until  they  are  completely  worked 
out  and  catalogued,  the  student  will  still  find  the  standards  of 
Wolff  or  Armsby  helpful  in  formulating  rations. 


CHAPTER  XI 

FOOD  REQUIREMENTS  OF  ANIMALS 

The  young  growing  animal.  The  distinct  and  characteristic 
feature  of  the  growth  of  young  animals  is  the  rapid  formation 
of  soft  tissue  and  bo-ne.  For  this  purpose  there  must  ~be  an 
abundant  supply  of  protein  and  suitable  ash. 

This  is  true  for  all  young  domestic  animals.  The  daily  in- 
crease in  live  weight  of  a  well  nourished  calf  is  very  considerable 
and  may  be  as  large  as  that  of  a  well-fed,  mature  steer.  It  may 
amount  to  2  pounds  per  day ;  and  much  less  than  this  would  be 
regarded  as  unsatisfactory.  Lawes  and  Gilbert  analyzed  the  en- 
tire body  of  a  fat  calf  with  the  following  results: — 

Per  cent 

Water 64.6 

Ash    4.8 

Protein    16.5 

Fat    14.1 

Based  on  this  analysis  the  daily  increase  of  2  pounds  live  weight 
in  a  growing  calf  would  mean  a  storage  of  about  0.33  Ib.  of  pro- 
tein and  0.28  Ib.  of  actual  fat,  or  a  total  increase  of  0.61  Ib.  of 
dry  body  material.  This  may  be  equal  to  one-fifth  or  more  of 
the  total  dry  substance  of  the  ration.  European  investigations 
with  calves  have  shown  that  one  pound  of  milk  solids,  practically 
all  digestible,  produced  one  pound  of  increase  in  live  weight. 
Because  of  the  water  content  of  this  increase,  the  actual  dry  mat- 
ter is  equal  to  about  one-third  of  a  pound.  Further,  these  studies 
showed  that  70  per  cent  of  the  protein  of  the  food  was  retained 
in  the  bodies  of  the  calves  and  72  per  cent  of  the  phosphoric  acid 
and  97  per  cent  of  the  lime  held  for  skeleton  and  tissue  expan- 
sion. On  an  assumed  consumption  of  10  pounds  of  average  milk 
daily,  this  would  mean  a  retention  of  6.4  grams  ( approximately 
one-fifth  of  an  ounce)  of  phosphoric  acid  and  8.7  grams  of  lime. 

In  this  country,  experiments  with  young  lambs  fed  cow's  milk 


260 


Agricultural  Chemistry 


showed  a  gain  in  live  weight  of  one  pound  for  every  5.8  pounds 
of  milk  consumed.  If  the  milk  contained  13  per  cent  of  dry 
matter,  then  0.75  pound  of  milk  sol  ids  produced  1  pound  of  in- 
crease. This  is  a  high  food  efficiency  and  practically  ten  times 
that  shown  with  animals  somewhat  mature.  This  serves  to  illus- 
trate the  rapid  increase  in  tissue  during  the  early  periods  of 
growth. 

The  kind  of  food  most  appropriate  to  the  wants  of  the  young 
animal  is  revealed  by  the  composition  of  milk.  The  first  milk 
secreted  by  the  mother,  colostrum,  is  very  rich  in  protein,  often 
containing  as  high  as  15  per  cent.  This  gradually  changes  after 
parturition  and  after  a  lapse  of  8  to  10  days  the  composition  of 
the  secretion  becomes  normal.  Below  is  given  the  composition 
of  colostrum  and  the  normal  milk  of  our  common  farm  animals. 


Percentage  Compos'.tion  of  Colostrum  Mvlk 


Nu- 

Water 

Protein 

Fat 

Sugar 

Ash 

tritive 

rat.o 

Ewe  

66.4 

16.6 

10.8 

5.0 

1.2 

1:1.8 

Sow  

70.1 

15.6 

9.5 

3.8 

0.9 

1:1.6 

Cow  

74.7 

17.6 

3.6 

2.6 

1.5 

1:0.6 

Percentage  Composition  of  Milk 


Ewe  

80.8 

4.9 

6.9 

4.9 

.84 

1:3.1 

Sow  

84.6 

5.2 

4.8 

3.2 

.80 

1:2.2 

Cow  

87.0 

3.5 

3.9 

4.8 

.70 

1:3.7 

Mai  e  

90.8 

2.0 

1.2 

5.6 

.40 

1:3.9 

The  solid  matter  of  milk  has  a  high  feeding  value,  because  of 
its  complete  utilization  by  the  animal.  It  also  supplies  an  abun- 
dant amount  of  ash  material  for  skeleton  and  tissue  formation. 
That  each  species  has  provided  for  the  young  a  milk  of  such  pro- 


Food  Requirements  of  Animals  261 

tein  and  ash  content  as  will  meet  the  rate  of  development  char- 
acteristic for  that  species  is  seen  in  the  following  table : — 

Days  required 
Protein  Ash  to  double  weight 

Ewe 4.9  per  cent  0.84  per  cent  15 

Sow   5.2         "  0.80         "  14 

Cow 3.5         "  0.70        "  47 

Mare   2.0        "  0.40        "  60 

Human   1.6        "  0.20        "  180 

This  is  a  very  suggestive  relation  of  the  protein  and  ash  con- 
tent of  milk  to  the  rate  of  growth  and  serves  to  illustrate  the 
necessity  of  maintaining  a  liberal  supply  of  these  materials  in 
easily  available  form  for  the  growing  young.  It  is  also  neces- 
sary to  remember  that  approximately  50  per  cent  of  the  ash  of 
milk  is  made  up  of  the  bone-forming  constituents,  lime  and  phos- 
phoric acid.  This  emphasizes  the  desirability  of  maintaining  the 
supply  of  these  ash  constituents  in  the  feed  of  the  animal  as  the 
mother's  milk  is  withdrawn  and  other  feeds  substituted. 

Supply  of  ash  material  necessary.  Probably  no  class  of  farm 
animals  is  exposed  to  as  much  danger  in  this  regard  as  the  pig. 
Abundant  supplies  of  lime,  in  particular,  are  contained  in  the 
hays  and  leafy  parts  of  plants,  but  these,  normally,  do  not  form 
a  part  of  the  ration  of  this  species  of  farm  animals.  The  grains 
are  low  in  lime;  and  even  wheat  bran,  so  often  accredited  with 
abundant  bone  forming  materials,  is  relatively  low  in  lime.  It 
contains  an  abundant  supply  of  phosphorus,  and  in  so  far  as 
the  supply  of  this  element  is  concerned,  normal  rations  for  all 
classes  of  farm  animals,  of  which  the  grains  and  particularly 
wheat  bran  form  a  part,  will  generally  supply  a  sufficient  quan- 
tity. In  furnishing  an  abundant  natural  supply  of  lime  to  the 
growing  animal,  recourse  may  be  had  to  the  legume  hays  for 
ruminants  or  the  ground  meal  from,  alfalfa  or  clover  hay  for  the 
young  pig. 

The  meadow  hays  are  also  rich  in  lime,  but  do  not  contain  as 
much  as  the  legume  hays.  The  beneficial  use  of  wood  ashes,  as 


262  Agricultural  Chemistry 

a  supplement  to  corn  in  the  ration  of  pigs,  probably  lies,  in  part 
at  least,  in  its  high  lime  content.  The  use  of  artificial  sources  of 
lime  for  growing  animals  of  all  classes,  where  the  natural  sources 
are  not  available,  is  highly  justifiable.  Probably  lime  as  a  phos- 
phate serves  this  purpose  best,  and  either  what  is  called  pre- 
cipitated calcium  phosphate  or  the  crude,  finely  ground  phosphate 
known  as  "floats"  can  be  used  to  advantage.  About  14  to  y%  of 
an  ounce  per  100  pounds  of  live  weight  during  the  rapidly  grow- 
ing periods  should  serve  the  purpose  of  building  a  strong  skeleton. 


The  effect  of  improperly  balanced  rations  on  growing  animals.     The 
ration  fed  these  pigs  was  too  low  in  phosphorus. 

No  attempt  is  made  here  to  give  directions  for  feeding  animals; 
this  must  be  sought  for  in  texts  wholly  devoted  to  that  subject. 
Only  a  few  of  the  more  fundamental  principles  are  discussed. 

Dangers  from  too  rich  milk.  In  recognizing  the  mother's 
milk  as  supplying  the  nutrients  in  the  best  forms  and  propor- 
tions, it  is  necessary  to  add  that  milks  very  rich  in  fat  have  been 
found  to  cause  intestinal  disturbances  and  impaired  nutrition. 
This  is  not  only  true  of  cow's  milk  fed  the  calf,  but  also  true 
when  that  milk  is  fed  to  pigs  or  to  the  human  infant. 

The  following  explanation  for  this  harmful  effect  of  excess  of 
fat  in  the  food  has  been  offered: — The  general  capacity  of  an 
organism  for  the  absorption  of  fat  is  strictly  confined  within  nar- 
row limits  and  consequently  an  excessive  supply  is  not  absorbed, 


Food  Requirements  of  Animals  263 

but  remains  in  the  intestine.  There  it  is  converted  into  soaps, 
composed  of  part  of  the  fat  and  an  alkali,  and  as  such  eliminated 
from  the  body  in  the  excreta.  This  excretion  of  soap  entails  to 
the  body  a  heavy  loss  of  alkaline  bases,  which  when  continued  for 
some  time  results  in  disturbed  nutrition.  On  an  exclusive  milk 
diet  containing  3.5  per  cent  of  fat  the  supply  of  alkaline  bases  is 
only  sufficient  for  normal  development  and  the  production  of  fat- 
rich  milk  in  cows  is  not  attended  by  a  corresponding  increase  in 
the  ash  forming  materials.  Rich  milk  is  the  result  o-f  breeding  by 
man  and  is  not  a  condition  original  to  the  milk  of  the  cow. 

Another  important  fact  to  bear  in  mind  is  that  the  capacity  to 
digest  the  starchy  grains  and  similar  substances  is  somewhat  un- 
developed in  the  very  young  animal  and  that  the  ferments  neces- 
sary for  this  purpose  are  probably  not  yet  very  abundant.  For 
this  reason  the  first  substitute  for  milk  should  not  consist  too 
largely  of  cereal  grains,  or  concoctions  of  insoluble,  starchy  ma- 
terials. Bulky,  fibrous  food  is  likewise  unsuitable  for  th'e  young* 
animal.  The  digestive  tract  of  calves  and  colts  must  gradually 
expand  before  the  coarse  hays  can  form  a  large  part  of  their 
ration. 

Influence  of  food.  In  experiments  on  the  influence  of  food 
upon  the  development  of  the  animal  body,  some  interesting  re- 
sults have  been  recorded.  Sanborn  and  Henry  fed  to  swine  ra- 
tions varying  considerably  in  the  protein  and  ash  supply.  Com- 
parisons of  middlings  and  blood  against  corn  meal  alone,  or 
shorts  and  bran  against  potatoes,  tallow  and  corn  meal,  Showed 
considerable  differences  in  the  development  of  the  animal.  Those 
fed  high  nitrogenous  rations  contained  more  blood  than  the 
others,  while  such  organs  as  the  kidney  and  liver  were  larger  in 
proportion  to  the  weight  of  the  body,  the  bones  stronger,  and  the 
proportion  of  muscle  greater.  These  were  extreme  rations,  and 
not  likely  to  occur  in  practice,  but  the  experiment  serves  the  pur- 
pose of  emphasizing  the  necessity  of  an  abundant  supply  of  pro- 
tein and  ash  material  for  the  growing  young.  Swine  fed  on  corn 
and  gluten  feed,  against  corn,  gluten  feed  and  "floats"  have 


264  Agricultural  Chemistry 

shown  marked  differences  in  the  skeleton  development.  In  this 
experiment  the  proteins  were  abundantly  supplied  in  both  ra- 
tions, but  only  in  the  second  was  there  a  liberal  supply  of  lime 
and  phosphoric  acid.  Where  such  a  supply  was  maintained  the 
skeletons  were  large  and  strong. 

Jordan  fed  two  lots  of  steers  from  calf-hood  on  rations  widely 
different  in  their  nutritive  ratio.  The  one  lot  received  for  grain, 
oil  meal,  wheat  bran  and  corn  meal,  and  the  other  lot  corn  meal, 
with  a  minimum  proportion  of  wheat  bran.  A  nutritive  ratio  of 
1 :5.2  and  1 :9.7  was  maintained.  At  the  end  of  17  months  and 
27  months,  one  animal  from  each  lot  was  killed  and  the  entire 
body,  exclusive  of  hide,  analyzed.  There  was  no  material  differ- 
ence in  the  composition  of  the  animals.  "The  amount  of  growth 
was  at  first  more  rapid  with  the  more  nitrogenous  ration,  but  the 
kind  of  growth  appeared  to  have  been  controlled  by  the  some- 
what fixed  constitutional  habits  of  the  breed."  (Jordan.) 

It  is  sometimes  claimed  by  practical  men  that  feeds  rich  in 
bone-forming  materials  should  be  withheld  from  the  pregnant 
mother;  that  such  feeds  are  conducive  to  large  boned  offspring, 
making  it  difficult  for  the  young  to  be  born.  Little  data  on  this 
question  are  available,  but  from  some  experiments  on  swine  at 
the  Wisconsin  Station,  there  is  no  evidence  that  excessive  sup- 
plies of  bone-forming  materials  influence  the  size  or  the  ash  eon- 
tent  of  the  skeleton  of  the  newly  born.  It  appears  that  the  power 
to  maintain  a,  constant  composition  for  the  foetus,  independent  of 
wide  variatio-ns  in  food  supply,  lies  inherent  in  the  mother. 

The  adult  animal  and  food  for  maintenance.  The  food  of  an 
adult  animal,  neither  gaining  nor  losing  in  weight,  is  used  for 
renewal  of  waste  tissue,  the  growth  of  hair,  horn  and  wool,  and 
for  the  production  of  heat  and  mechanical  work.  The  work  per- 
formed consists  in  the  muscular  movements  involved  in  chewing 
and  moving  the  food  along  the  intestinal  tract;  muscular  move- 
ments of  the  heart  in  pumping  the  blood;  respiration  and  the 
metabolic  activity  of  the  cells  in  causing  the  chemical  transforma- 
tions of  the  nutrients.  This  is  internal  work.  It  has  been  cal- 


Food  Requirements  of  Animals 


265 


culated  that  the  power  exerted  daily  by  the  heart  of  a  man  150 
Ibs.  in  weight,  would  raise  1  ton  to  a  height  of  242  feet.  Then 
in  addition,  there  is  always  some  work  done  in  moving  the  body 
from  place  to  place.  A  horse  of  1100  pounds  weight,  walking  20 
miles  on  level  ground,  and  without  a  load,  will  do  work  equivalent 
to  raising  2328  tons  1  foot.  The  internal  work  finally  appears 
largely  as  heat,  while  in  the  external  movements  of  the  body, 
probably  70  per  cent  of  the  total  energy  developed  in  the  muscles 
appears  as  heat. 

The  smaller  the  animal  the  greater  the  loss  of  heat  per  unit  of 
weight,  and  consequently  the  more  liberal  must  be  the  supply  of 
food.  This  is  because  small  bodies  have  in  proportion  to  their 
weight,  a  much  greater  surface.  Thus,  heat  is  lost  by  radiation 
from  the  surface  of  the  body  and  in  evaporating  the  water  ex- 
haled through  the  lungs  and  skin. 

In  the  following  table  the  heat  production  in  resting  animals 
is  given : — • 

Heat  Production  in  Resting  Animals 


Horse  . 
Pig.... 
Dog . . . 
Goose  . 
Mouse. 


Weight 
in  pounds 


970.0 

281.0 

33.0 

7.7 
0.03 


Calories  prodvced 

Per  pound 

Per  eq.  mm. 
surface 

24.8 
42.0 
103.0 
146.7 
466.0 

948 
1078 
1039 
943 
917 

This  shows  that  animals  will  produce  heat  in  proportion  to 
their  surface ;  it  is  interesting  to  note  that  in  the  standard  rations 
for  animals,  the  quantity  of  food  increases  at  nearly  the  same 
ratio  as  the  surface  increases.  For  example,  while  the  oxen  in 
growing  from  a  weight  of  165  to  935  pounds  increases  in  weight 


266  Agricultural  Chemistry 

5.7  times,  the  surface  of  the  animal  increases  but  3.2  times  and 
the  food  required,  3.5  times. 

It  is  essential  that  the  maintenance  ration  should  supply  enough 
protein  to  replace  the  daily  waste  of  the  nitrogenous  tissue.  Only 
a  small  amount  is  necessarily  destroyed  by  the  resting  animal^ 
but  there  is  a  constant  waste,  and  unless  this  is  replaced  the 
animal  will  die  of  starvation.  It  is  plain  then  that  the  demands 
upon  food  for  maintenance  purposes  are  mainly  for  the  produc- 
tion of  muscular  energy  and  heat.  Armsby  found  that  a  supply 
of  0.6  Ib.  of  digestible  protein  per  day  was  sufficient  for  the 
permanent  maintenance  of  a  1000  pound  ox,  receiving  a  ration 
with  a  nutritive  ratio  of  1 :11. 

The  thorough  studies  of  Zuntz  on  the  horse  have  shown  that  a 
1000  pound  animal  can  be  maintained  on  6.4  pounds  of  available 
nutrients,  provided  the  total  ration  does  not  contain  more  than 
three  pounds  of  crude  fiber.  This  means  that  the  nutrients  must 
come  from  hay  and  grain.  Grandeau  places  the  maintenance  re- 
quirement for  the  same  weight  of  animal  at  7  to  7.8  pounds  of 
digestible  organic  matter,  including  0.45  pound  of  digestible  pro- 
tein. 

There  are  few  experiments  with  sheep,  but  according  to  Ger- 
man experiments,  11.8  pounds  of  digestible  organic  matter,  in- 
cluding 1.0  pound  of  digestible  protein,  per  1000  pounds  live 
weight  are  required  to  maintain  proper  conditions.  Its  con- 
tinued production  of  wool,  higher  temperature  and  smaller  size 
make  the  requirements  for  this  animal  somewhat  more  liberal 
than  with  the  horse  or  ox. 

It  is  clear  then  that  90  per  cent  or  more  of  a  maintenance  ration 
may  consist  of  carbohydrates  or  materials  used  solely  for  fuel. 
This  makes  it  easy  to  supply  this  ration  from  the  home  grown 
products.  The  quantity  of  available  nutrients  consumed  is  small 
and  may  largely  be  made  up  of  coarse  material,  such  as  corn 
fodder  and  hay.  Again,  the  low  protein  requirement  and  the 
possibility  of  a  wide  nutritive  ratio,  characteristic  of  home  grown 
products,  makes  its  selection  easy. 


Food  Requirements  of  Animals  267 

Requirements  for  labor.  As  the  horse  is  practically  the  only 
animal  used  in  this  country  for  draft  and  road  purposes,  it  will 
be  considered  alone  in*  this  connection.  The  source  of  the  energy 
evolved  during  labor  and  appearing  as  extra  work  and  heat  must 
come  from  the  oxidation  of  food.  If  work  is  to  be  performed 
and  at  the  same  time  body  weight  remain  constant,  the  quantity 
of  food  must  be  increased. 

It  was  supposed  at  one  time  that  muscular  effort  was  produced 
by  the  oxidation  of  the  nitrogenous  constituents  of  the  muscle, 
and  that  a  ration  very  rich  in  protein  was  necessary,  if  hard  work 
was  to  be  maintained.  This  idea  is  now  known  to  be  erroneous. 
Men  have  climbed  mountains  and  measured  the  excretion  of  urea 
(the  principal  nitrogenous  constituent  of  the  urine)  during  such 
severe  exercise.  There  was  no  important  increase  in  its  produc- 
tion under  such  conditions.  Increased  work  increases  the  excre- 
tion of  carbon  dioxide  but  not  of  nitrogen.  In  other  words,  the 
carbohydrates  and  fats  are  largely  the  fuel  materials  that  furnish 
energy  for  mechanical  purposes. 

Zuntz  has  determined  the  quantity  of  food  which  a  horse  needs 
in  order  to  perform  work  under  varying  conditions.  "A  horse 
weighing  with  harness  1144  pounds,  will  require  1.33  pounds  of 
available  food  to  walk  10  miles  at  2l/2  miles  per  hour ;  1.69  pounds 
when  walking  the  same  distance  at  a  speed  of  3V3  miles  per  hour ; 
and  2.53  pounds  when  trotting  the  same  distance  at  7  miles  an 
hour."  This  is  important  knowledge  on  the  influence  of  speed 
upon  the  food  requirement  in  a  unit  of  time. 

The  pace  of  the  animal  is  another  important  factor.  Grandeau 
and  Leclerc  kept  a  horse  in  good  condition,  walking  l2l/2  miles 
a  day  with  a  daily  ration  of  19.4  pounds  of  hay,  but  when  the 
same  distance  was  done  trotting,  24  pounds  was  insufficient.  A 
horse  walking  the  above  distance  and  hauling  a  load  (equivalent 
in  additional  work  to  1943  foot-tons)  was  maintained  by  a  ration 
of  26.4  pounds  of  hay ;  but  when  the  same  work  was  done  trotting, 
a  daily  ration  of  32.6  pounds  of  hay,  which  was  all  it  would  eat, 
was  insufficient  to  maintain  weight.  Trotting  or  galloping  in- 


268  Agricultural  Chemistry 

volves  additional  internal  work;  the  animal  also  lifts  its  own 
weight  at  each  step,  which  only  appears  as  heat  as  it  falls  back 
again.  Consequently  horses  of  different  p< action"  will  require 
unlike  amounts  of  food  to  accomplish  the  same  task. 

When  a  horse  exerts  itself  to  the  utmost  the  consumption  of 
oxygen  rises  rapidly  and  the  food  consumed  per  unit  of  work 
may  be  nearly  twice  as  much  as  with  ordinary  draft.  A  slow 
pace,  consistent  with  conditions  involved,  will  be  economical  of 
food  consumption  per  unit  of  work  performed. 

Zuntz  found  that  the  requirements  for  a  horse,  plowing  8  hours 
a  day,  were  14.03  pounds  of  digestible  nutrients.  This  is  some- 
what less  than  the  requirement  found  in  the  German  standards 
of  Wolff  and  Lehmann.  According  to  these  formulas,  a  1000 
pound  horse  requires  11.4  pounds  of  digestible  food  daily  for 
moderate  work,  13.6  pounds  for  average  work,  and  16.6  pounds 
for  heavy  work.  These  standards  also  call  for  a  nutritive  ratio 
of  1 :7  to  1 :6,  dependent  upon  the  severity  of  the  labor.  On  the 
other  hand,  Lavalard,  recommends  that  1.15  pounds  of  digestible 
protein  daily  is  sufficient  for  ordinary  labor,  and  1.35  pounds 
when  the  labor  is  severe.  This  is  a  nutritive  ratio  not  far  from 
1 :10.  From  what  has  been  said  on  the  source  of  muscular  force, 
it  is  probable  that  the  nutritive  ratio  recommended  by  th&  Ger- 
man standard  is  narrower  than  need  be.  Horses  working  on  the 
sugar  plantations  of  the  Fiji  islands  receive  15  pounds  of  molasses 
per  day  and  a  nutritive  ratio  of  1 :11.8.  However,  a  fairly  good 
proportion  of  protein,  for  its  peculiar  and  characteristic  dynamic 
effect,  appears  advisable. 

It  is  the  opinion  of  Jordan  that  " rations  properly  com- 
pounded from  ordinary  farm  products,  such  as  silage,  roots, 
meadow  hay,  legume  hays  and  the  cereal  grains,  will  generally 
contain  protein  in  sufficient  proportion  and  will  seldom  need  re- 
inforcing with  the  commercial  nitrogenous  feeding  stuffs." 

If  a  horse  at  severe  labor  requires  16.6  pounds  of  digestible 
nutrients,  it  is  manifest  that  this  could  not  be  obtained  from  the 
coarse  fodders.  Concentrated  feeds  must  be  used.  Ten  pounds 


Food  Requirements  of  Animals  269 

of  hay  is  all  a  work  horse  should  consume  in  one  day.  We  have 
seen  that  the  production  value  of  the  coarse  feeds  is  not  as  large 
as  the  grains,  and  consequently  cannot  be  expected  to  furnish 
available  energy  for  severe  labor  in  sufficient  quantity,  compatible 
with  the  storage  capacity  of  the  digestive  apparatus  of  the  horse. 

There  has  been  a  strongly  established  opinion  'that  oats  are 
pre-eminently  the  horse  feed  and  must  form  a  generous  propor- 
tion of  the  grain  ration;  that  they  give  life  and  nerve  to  the 
animal.  At  one  time  the  discovery  of  a  special  compound, 
avenin,  resident  in  the  oat  kernel  and  endowed  with  these  stimu- 
lating properties,  was  announced.  This  is  now  disproved  and  it 
is  becoming  more  and  more  evident  that  other  grains  can  be  sub- 
stituted for  oats  with  no  impairment  to  the  animal's  well  being. 

Fattening  requirements.  To  increase  body  weight  it  is  neces- 
sary that  the  food  supply  be  in  excess  of  that  required  for  main- 
tenance and  for  the  production  of  heat  and  work.  "When  such 
an  excess  is  given,  the  protein  and  ash  are  in  part  converted  into 
new  tissue,  and  the  fats,  carbohydrates  and  possibly  proteins, 
stored  up  in  the  form  of  fat.  Feeding  a  young  animal  an  excess 
will  promote  the  further  development  of  bone  and  muscle,  while 
in  the  case  of  the  mature  animal,  the  increase  will  come  almost 
wholly  from  the  deposition  of  fat  in  the  tissues.  In  both  in- 
stances fat  forms  the  largest  proportion  of  the  increase.  This  is 
shown  in  the  following  figures : — 

Composition  of  Increase  When  Steers  are  Fattening 

Water  Ash         Protein          Fat 

Per  cent    Per  cent    Per  cent    Per  cent 

Oxen,  fattening  very  young. .  32-37          2.25  10  50-55 

Matured  animals,  final  period  25-30          1.5  7-8          60-65 

These  figures  serve  to  illustrate  how  the  food  is  used,  and  that 
the  increase  is  largely  fat  formation.  A  satisfactory  gain  of  2 
pounds  per  day  would  then  mean  a  storage  of  1.3  to  1.5  pounds 
of  dry  substance,  of  which  about  0.2  pound  is  protein.  From  the 
fact  that  carbohydrates  can  serve  as  sources  of  fat,  it  is  evident 


270  Agricultural  Chemistry 

that  the  non-protein  part  of  a  ration  may  be  the  chief  source  of 
the  increase  laid  on  by  a  fattening  animal.  The  protein  require- 
ment for  the  constructive  work  is  apparently  small.  It  would 
appear  from  this  that  the  nutrients  serving  mainly  for  fat  forma- 
tion need  not  come  from  proteins  in  the  ration,  but  rather  from 
the  fats  and  carbohydrates.  Further,  from  a  theoretical  point 
of  view,  this  would  lead  us  to  the  conclusion,  that  for  fairly  ma- 
ture fattening  animals  the  nutritive  ratio  may  be  wider  than  that 
recommended  in  the  German  standards.  These  standards  call 
for  a  ratio  of  from  1 :5  to  1 :7  in  the  various  classes  of  fattening 
farm  animals. 

Kellner,  from  experiments  on  oxen,  declares  that  a  fattening 
ration  may  vary  in  its  nutritive  ratio  from  1 :4  to  1 :10  without 
affecting  the  amount  of  increase  per  unit  of  digestible  matter, 
provided  the  nutrients  supplied  above  maintenance  come  from 
easily  digestible  feeding  stuffs.  Armsby,  in  his  standards  for 
fattening  steers,  provides  no  additional  protein  above  mainte- 
nance, only  allowing  additional  therms,  which  simply  represent 
material  for  fuel  and  fat  formation.  Certain  practical  feeding 
experiments  show  that  ivide  rations  have  been  as  effective  as  the 
narrower  ones.  On  the  other  hand  there  are  experiments  of  this 
class  which  show  more  rapid  gains  when  a  larger  proportion  of 
protein  was  furnished.  Possibly  these  are  to  be  explained  on  the 
basis  of  increased  palatability  and  variety  of  nutrients,  thereby 
securing  an  increased  consumption.  The  proportion  of  protein 
was  probably  a  minor  factor.  When  the  nutrients  supplied  se- 
cure palatability,  ease  of  digestion  and  bowel  regulation,  it  is 
probable  that  they  need  not  be  of  very  highly  nitrogenous  char- 
acter. 

Facts  bearing  on  this  point  are  disclosed  in  the  pig  feeding  ex- 
periments at  the  Rothamsted  Station  and  are  appended  in  the 
following  table. 

The  figures  in  the  last  column  are  not  the  nutritive  ratios, 
which  apply  to  digestible  matter,  but  simply  the  ratios  of  nitro- 
genous to  non-nitrogenous  matter.  The  true  nutritive  ratio  would 


Food  Requirements  of  Animals 


271 


be  considerably  wider.  The  results  clearly  show  that  100  pounds 
of  increase  were  produced  with  practically  the  same  consumption 
of  organic  matter,  notwithstanding  the  great  variations  in  the 
quantity  of  protein  supplied. 

In  the  case  of  sheep,  the  fattening  process  is  not  greatly  unlike 
that  of  steers,  the  increase  being,  however,  somewhat  richer  in 
fat. 

It  is  probable  then,  that  for  fattening  animals  a  nutritive  ratio 
somewhat  under  that  recommended  by  the  Wolff  standards  is  not 
inconsistent  with  successful  feeding.  However,  if  the  animal  is 
still  growing,  then  it  is  apparent  that  a  wide  ratio  is  not  con- 

Fattening  Pigs  on  Food  Rich  and  Poor  in  Protein 


Food   supplied 

Consumed  to  produce  100  Ibs. 
of  gain 

Ratio  of 
protein  to 
non- 
protein 

Protein 
substance 

Non- 
protein 
substance 

Total 
organic 
matter 

Beans  and  lentil  meal  

Lbs. 
137 
113 
81 
80 
72 
72 
58 

Lbs. 
291 
297 
329 
340 
338 

:;66 

362 

Lbs. 
428 
410 
410 
420 
410 
438 
420 

1:2.1 

1:2.6 
1:4.1 
1:4.2 
1:4.7 
1:5.1 
1:6.3 

Beans,  lentil  and  corn  

Starch,  Bugar,  lentil,  bran  
Starch,  lentil,  bran  

Corn,  bean,  lentil,  bran  

Corn,  bean  and  lentil  

Corn  and  bran  

ducive  to  best  results.  From  this  it  follows  that  the  home  grown 
fodders  and  grains  can  furnish  the  main  sources  of  the  nutrients 
required  for  fattening  purposes.  It  must  always  be  kept  in  mind, 
however,  that  mere  mathematical  formulas  should  not  form  the 
basis  for  calculating  supplies  for  the  living  organism.  The  feeder 
recognizes  the  value  of  a  little  oil  meal  and  middlings  in  keeping 
the  animal  in  "condition"  for  best  results,  but  it  is  not  to  be 
assumed  that  their  entire  value  lies  in  their  protein  content. 
The  economy  of  a  ration  may  not  always  depend  upon  its  capacity 


272 


Agricultural  Chemistry 


to  form  an  increase.  It  may  be  decidedly  to  the  farmer's  ad- 
vantage to  enrich  the  food  with  such  materials  as  bran  and  highly 
nitrogenous  foods  for  the  purpose  of  increasing  the  value  of  the 
manure  produced,  and  in  this  way  to  maintain  and  increase  the 
fertility  of  the  land. 

Before  leaving  this  subject  it  may  be  valuable  to  call  attention 
to  the  relative  efficiency  of  the  different  classes  of  farm  animals 
as  transformers  of  food  into  body  increase.  Warington  furnishes 
some  interesting  data  on  this  point: — 


• 

Per  1000  Ibs.  live  weight 
per  week 

Required  to  produce 
100  pounds  increase 

Dry 
matter 
consumed 

Digested 
organic 
matter 

Increase 
in  live 
weight 

Dry  food 
consumed 

Digested 
organic 
matter 

Oxen  

Lbs. 
125 
160 
270 

Lbs. 
88 
121 
227 

Lbs. 
11.3 
17.6 
64.3 

Lbs. 
1,109 
912 
420 

Lbs. 
777 
686 
353 

Sheep  

Pigs  

It  will  be  seen  that  in  proportion  to  its  weight,  the  sheep  eats 
more  food  and  yields  more  increase  than  the  ox,  while  the  pig 
consumes  more  food  and  returns  much  more  increase  than  either. 
This  is  due  to  the  concentrated  and  easily  digestible  character  of 
the  food  supplied  the  fattening  pig.  It  must  expend  compara- 
tively little  energy  in  preparing  the  material  for  assimilation. 
Again,  the  digestive  apparatus  of  ruminants  is  anatomically  dif- 
ferent from  that  of  the  pig.  In  the  former  the  capacity  for  the 
storage  of  rough  fodders  is  large,  but  the  proportion  of  intestine, 
where  absorption  is  most  active,  is  much  smaller  than  in  the  pig. 

Requirements  for  wool  production.  Wool  is  the  hair  of 
sheep ;  but  the  hair  of  certain  goats,  such  as  the  alpaca,  cashmere, 
and  mohair,  as  well  as  that  of  the  camel,  is  also  classed  as  wool. 
Wool  differs  from  ordinary  hair  only  in  its  physical  structure, 
being  covered  with  minute,  overlapping  scales,  and  having  a 


Food  Requirements  of  Animals  273 

twisted  or  curled  fiber.  Wool  has  great  affinity  for  water  and 
may  contain  from  8  to  12  per  cent  of  moisture  in  hot,  dry  weather, 
and  up  to  50  per  cent  in  damp  weather.  Raw  wool  consists  of 
(1)  yolk  or  wool-grease;  (2)  suint;  and  (3)  the  pure  wool  hair. 
The  first  two  may  constitute  from  30  to  80  per  cent  of  the  weight 
of  the  unwashed  wool.  The  yolk  is  made  up  of  fatty  or  wax-like 
bodies,  of  complex  composition  and  insoluble  in  water.  In  a 
washed  fleece  the  yolk  may  vary  from  more  than  30  per  cent  to 
less  than  8  per  cent.  Short  fine  wool  contains  the  largest  pro- 
portion of  yolk.  The  suint  is  an  excretion  of  the  perspiration 
glands  of  the  skin  and  consists  of  potassium  salts  of  fatty  acids, 
together  with  phosphates,  sulphates  and  chlorides.  It  is  soluble 
in  water  and  consequently,  removed  by  washing.  It  may  amount 
to  50  per  cent  of  the  weight  of  unwashed  wool,  but  with  a  sheep 
exposed  to  the  weather,  the  quantity  may  be  15  per  cent  or  less. 
The  pure  wool  fiber  is,  for  the  most  part,  a  protein  and  contains 
about  16  per  cent  of  nitrogen  and  3.6  per  cent  of  sulphur.  A 
large  proportion  of  the  nitrogen  of  a  sheep 's  body  is  found  in  the 
wool.  The  fact  that  wool  production  is  at  the  expense  of  proteins 
must  indicate  that  a  somewhat  narrower  ration  is  demanded  than 
for  mere  fattening.  Wolff  fed  two  sheep  on  rations  consisting  of 
hay  and  bean  meal,  which  supplied  proteins  liberally  and  main- 
tained the  weights  of  the  animals.  Two  others  received  at  the 
same  time,  oat  straw  and  roots,  and  lost  slightly  in  weight.  The 
yield  of  pure  wool  fiber  in  the  first  case  was  12.9  pounds  and  in 
the  second  10.0  pounds.  It  appears  from  this  that  under  poor 
treatment  the  yield  of  wool  will  be  seriously  diminished.  Ex- 
periments further  show  that  on  liberal  fattening  rations,  the  pro- 
duction of  wool  is  no  greater  than  when  the  ration  is  just  suf- 
ficient to  maintain  the  animal.  However,  from  the  experiments 
of  others,  it  appears  that  on  somewhat  scanty  rations,  the  body 
may  lose  weight  without  the  production  of  wool  being  seriously 
affected.  All  this  emphasizes  the  fact  that  for  the  health  and 
vigor  of  the  animal  producing  this  nitrogenous  coat,  the  protein 
supply  must  not  fall  too  low. 


274  Agricultural  Chemistry 

The  high  favor  in  which  such  root  crops  as  turnips  and  ruta- 
bagas are  held  by  sheep  feeders  may  find  its  explanation  in  their 
richness  in  sulphur,  which  we  have  seen  constitutes  a  considerable 
proportion  of  the  pure  wool  fiber. 

Requirements  for  milk  production.  Milk  ultimately  comes 
from  the  food  and  its  direct  purpose  is  for  the  nutrition  of  the 
young.  For  this  reason  its  production,  so  far  as  possible,  is  made 
independent  of  the  immediate  food  supply.  If  the  surplus  food 
given  a  fattening  ox  is  withdrawn  to  a  maintenance  requirement, 
the  laying  on  of  increase  will  immediately  cease ;  but  the  food  of 
a  milking  cow  may  be  reduced  to  maintenance,  without  stopping 
the  production  of  milk.  The  animal  will  continue  to  produce 
milk,  drawing  for  its  source  from  her  own  body.  The  quantity 
produced  will  decrease  and  the  animal  will  steadily  grow  thinner. 
A  minimum  food  supply  will  not  entirely  stop  milk  production, 
neither  will  an  over-abundant  supply  raise  the  milk  production 
beyond  certain  limits.  Each  cow  has  an  inherent  milk  produc- 
ing capacity,  determined  by  breed  and  individuality.  Above 
this  it  is  rarely  possible  to  go,  but  whether  this  capacity  is  reached 
will  depend  upon  food  and  treatment.  Excess  of  food  will  simply 
tend  to  fatten.  Generous  feeding  will  not  make  a  good  milch  cow 
out  of  a  poor  one,  but  it  will  sustain  a  full  flow  of  milk  and  ex- 
tend the  period  of  profitable  production. 

There  is  only  one  way  to  determine  whether  a  cow  is  profitable, 
and  that  is  by  determining  her  yield  of  milk  and  the  amount  of 
marketable  constituents  it  contains.  To-day,  this  is  entirely  done 
on  the  basis  of  the  quantity  of  fat  the  milk  contains,  which  gives 
the  animal's  capacity  for  butter  production.  To  measure  the 
capacity  of  her  milk  for  cheese  production,  both  fat  and  casein 
must  be  determined.  From  the  standpoint  of  economy  in  trans- 
forming feed  stuffs  into  human  food,  the  total  milk  solids,  and 
not  the  milk  volume,  should  be  the  basis  for  estimation. 

The  quantity  of  nutrients  necessary  to  make  100  pounds  of 
Jersey  milk,  other  things  being  equal,  is  greater  than  that  re- 
quired to  produce  the  same  weight  of  Holstein  milk.  From  the 


Food  Requirements  of  Animals  275 

standpoint  of  the  farmer  the  most  profitable  cow  is  the  one  pro- 
ducing the  largest  return  in  butter  fat,  butter  fat  and  casein,  or 
total  milk  solids  per  unit. of  food  consumed. 

The  transformation  of  digestible  feed  material  into  human 
food  by  the  dairy  cow  far  exceeds  that  produced  in  the  same  time 
by  the  growing  or  fattening  ox  and  slightly  exceeds  that  produced 
in  swine.  An  ox,  gaining  2  pounds  per  day,  will  yield  in  edible 
solids  about  1.5  pounds,  while  a  dairy  cow,  producing  30  pounds 
of  milk  containing  12  per  cent  of  solids,  will  yield  3.6  pounds. 
Based  on  pounds  of  digestible  nutrients  consumed,  Jordan  has 
given  us  some  interesting  figures.  They  are  general  averages 
and  are  given  in  the  following  table ;  they  represent  the  pounds 
of  edible  solids  produced  by  100  Ibs.  of  digestible  organic  matter 
in  the  ration. 

Relation  of  Food  to  Produce 

Edible  solids 
Lbs. 

Milk 18.0 

Steers,  (carcass)  2.52 

Lambs 2.60 

Swine 15.60 

Calves 8.10 

Fowl 4.20 

Eggs 5.10 

The  quantity  of  solids  in  the  cow 's  milk,  per  unit  of  feed  con- 
sumed, thus  always  exceeds  the  quantity  of  solids  produced  in 
the  increase  of  the  fattening  ox,  and  in  the  order  of  food  ef- 
ficiency the  cow  leads  the  list. 

Milk  is  a  highly  nitrogenous  substance,  and  its  proteins  must 
be  made  from  protein.  They  can  have  no  other  ultimate  source 
but  the  feed  and  cannot  be  produced  from  fats  or  carbohydrates. 
Thirty  pounds  of  average  milk  will  contain  a  pound  of  protein. 
This  daily  drain  means  that  the  ration  of  the  dairy  cow  must  be 
reasonably  narrow.  If  0.6  pound  of  protein  is  needed  for  main- 
tenance, then  1.6  pounds  must  be  used  daily.  Practice  and  sci- 
ence have  established  the  quantity  of  digestible  organic  matter 
necessary  for  economical  milk  production  at  from  15.5  to  16.5 


276  Agricultural  Chemistry 

pounds  per  day  for  a  good  cow  of  average  size.  The  quantity  re- 
quired may  vary  somewhat  according  to  size, — a  small  cow  re- 
quiring proportionately  somewhat  more  than  a  larger  one  for  the 
same  yield  of  milk, — but  capacity  for  production  is  the  more  im- 
portant factor  in  determining  the  quantity  of  feed  required. 
With  that  amount  of  digestible  nutrients,  the  nutritive  ratio 
would  be  about  1 :9.5.  Careful  experiments,  however,  show  that 
a  nutritive  ratio  of  1 :5.5  to  1 :6.5  is  more  efficient  than  the  wider 
one,  and  that  a  cow  of  average  size  and  good  capacity  should  re- 
ceive at  least  2.25  pounds  of  digestible  protein  daily,  with  a  nu- 
tritive ratio  not  wider  than  1 :6.5.  Young  pasture  grass,  well 
known  to  be  an  efficient  milk  producer,  is  even  narrower  than  this. 
The  function  of  this  additional  protein  is  not  known,  but  the  ac- 
cepted axiom  that  proteins  stimulate  the  metabolic  activities  of 
the  cells  is  borne  out  here,  with  an  intensified  milk  secretion  as 
the  result.  On  the  other  hand,  excessive  protein  feeding  may 
be  injurious  and  certainly  is  not  necessary. 

It  has  been  taught  that  the  fats  of  milk  originate  from  the 
protein  and  food  fats.  If  true,  this  would  increase  the  demand 
for  protein,  but  experiments  have  clearly  demonstrated  that  they 
are  not  a  necessary  source  of  milk  fat.  In  a  carefully  conducted 
experiment  at  the  New  York  Experiment  Station,  Jordan  con- 
clusively showed  that  the  carbohydrates  of  the  food  could  serve 
as  milk-fat  formers. 

The  food  consumed  by  the  dairy  cow  during  the  first  half  of 
the  lactation  period  is  largely  used  in  milk  production,  but  dur- 
ing the  latter  portion  of  lactation  it  is  partly  consumed  in  build- 
ing the  calf,  and  the  return  in  milk  is  reduced.  A  newly-born 
calf  weighing  80  pounds,  may  contain  20  pounds  of  protein,  3 
pounds  of  fat,  and  the  rest  will  be  water  and  ash. 

From  what  has  been  said  on  the  necessity  of  a  proper  protein 
supply  for  the  milch  cow,  it  is  apparent  that  where  the  home 
grown  crops  are  the  hays  made  from  true  grasses  and  where  the 
corn  crop  is  the  chief  one  raised,  then  home-grown  rations  for 
maximum  efficiency  in  milk  production  are  not  possible.  Where, 


Food  Requirements  of  Animals  277 

however,  alfalfa  and  clover  make  the  hay,  and  peas  and  oats  are 
grown,  a  protein  supply  consistent  with  efficiency  can  be  pro- 
duced. 

There  is  the  additional  fact  that  the  production  of  milk  de- 
mands a  plentiful  ash  supply  to  the  animal.  Thirty  pounds  of 
milk  will  contain  nearly  an  ounce  of  lime  and  the  same  quantity 
of  phosphoric  acid.  Besides  the  quantities  secreted  in  the  milk, 
there  is  apparently  a  waste  from  cell  activity,  which  in  the  case 
of  a  dairy  cow  yielding  30  pounds  of  milk,  was  found  to  be  nearly 
equal  to  the  quantity  secreted  in  the  milk.  In  an  experiment  at 
the  Wisconsin  Station,  where  a  ration  was  made  up  of  oat  straw, 
rice,  wheat  bran  and  wheat  gluten,  a  cow  continued  to  give  a  milk 
of  constant  composition  in  respect  to  lime  content,  as  well  as  all 
other  constituents;  yet  the  amount  of  lime  supplied  the  animal, 
for  a  period  of  over  100  days,  had  been  deficient.  To  maintain  a 
normal  composition  of  the  milk,  the  animal  had  withdrawn  lime 
from  her  skeleton,  a  remarkable  transmigration  of  material.  The 
health  of  the  animal  was  apparently  unimpaired,  but  it  is  self- 
evident  that  ultimately  the  milk  flow  must  have  ceased  or  the 
animal  would  have  collapsed.  While  the  ration  used  was  unus- 
ual, the  experiment,  however,  emphasizes  the  necessity  of  a  liberal 
supply  of  ash  material  for  the  dairy  cow.  The.  legume  seeds  and 
cereal  grains  are  low  in  lime,  but  are  fairly  rich  in  phosphorus. 
Wheat  bran  is  relatively  poor  in  lime,  but  rich  in  pJwsphorus. 
Ten  pounds  of  bran  will  supply  about  one-fourth  of  an  ounce  of 
lime,  but  nearly  one-third  of  a  pound  of  phosphoric  acid.  The 
hays  from  the  true  grasses  are  fairly  well  supplied  with  lime, 
but  the  legume  hays,  as  clover  and  alfalfa,  are  particularly  rich 
in  this  material,  and  should,  for  this  reason,  form  a  part  of  the 
ration  of  the  dairy  cow.. 

It  would  appear,  then,  that  in  most  rations  recognized  by  dairy- 
men as  efficient  for  milk  production,  phosphoric  acid  and  lime 
will  be  plentifully  supplied,  especially  where  bran  and  the  legume 
hays  constitute  a  part  of  the  ration.  But  should  straws  form  the 
roughage,  the  supply  of  lime  may  become  deficient. 


CHAPTER  XII 

MILK  AND  ITS  PRODUCTS 

Milk  is  a  valuable  agricultural  product  and  both  it  and  the 
products  obtained  from  it  are  of  considerable  commercial  and  in- 
dustrial importance.  The  dairy  products  of  the  State  of  Wiscon- 
sin alone  are  valued  at  $100,000,000. 

Secretion.  Milk  is  the  secretion  of  special  glands  in  the  mam- 
malian female  and  adapted  to  the  nourishment  of  the  newly  born 
young  of  that  particular  species.  The  constituents  of  the  milk 
are  especially  elaborated  by  the  cells  of  the  mamma;  these  con- 
stituents do  not  exist  preformed  in  the  blood,  but  are  formed  by 
profound  chemical  processes,  little  understood,  out  of  the  nu- 
trients carried  in  the  blood  to  the  active  cells.  For  example,  no 
casein  or  milk  sugar  exists  either  in  the  food  of  the  cow  or  in  her 
blood,  but  from  the  nitrogenous  constituents  of  blood,  the  com- 
plex protein,  casein,  is  elaborated;  also,  from  the  simple  sugar 
dextrose,  the  more  complex  milk  sugar  is  formed.  This  is  all 
accomplished  through  the  wonderful  activities  of  the  udder  cells. 
That  the  composition  of  the  milk  is  closely  related  to  the  food  re- 
quirements of  the  newly  born  young  and  its  rate  of  growth,  has 
been  suggested  by  the  physiologist,  Bunge.  This  relates  partic- 
ularly to  the  ash  and  protein  materials  of  milk,  which  are  so 
necessary  for  the  life  processes  and  the  rapid  building  of  the 
growing  young. 

The  following  table  will  clearly  show  that  the  ash  of  milk  and 
of  the  new  born  young  are  very  much  alike,  while  they  have  an 
entirely  different  composition  from  the  fluid  out  of  which  they 
are  formed,  namely  the  blood,  and  especially  the  blood  serum; 
from  a  consideration  of  such  facts,  it  appears  certain  that  the 
cells  of  the  milk  gland  must  possess  the  power  of  selection  and 
that  milk  is  not  merely  filtered  from  the  blood. 


Milk  and  Its  Products 


279 


Comparative  Composition  of  the  Milk,  Blood  and  Body 
of  the  Same  Animal 


100  parts  by  weight  of  ash  contained  in  gramr 

Dog  a  few 
hours  old 

Dog's  milk 

Dog's  blood 

Dog's  blood 
serum 

Potash  

11.14 
10.6 
29.5 
1.8 
39.4 

15.0 
8.8 
27.2 
1.5 
34.2 

3.1 
45.6 
0.9 
0.4 
13.3 

2.4 
52.1 
2.1 
0.5 
5.9 

Soda  

Lime  

Magnesia  

Phosphoric  acid  

If  we  compare  the  time  required  by  the  suckling  to  double 
its  weight  at  birth,  with  the  amounts  of  protein  and  ash — per- 
haps the  most  essential  constituents  for  the  formation  of  tissue — 
contained  in  100  parts  of  milk,  it  is  evident  at  a  glance  that  the 
amounts  of  these  increase  in  proportion  to  the  rate  of  growth  of. 
the  animal.  This  is  shown  in  the  following  table : — 

Composition  of  Milk  Ash  from  Different  Animals 


Species 

Days 
required 
to  double 
weight 

100  parts  by  weight  of  milk 
contains  in  grams 

Protein 

Ash 

Lime 

Phos- 
phoric 
acid 

Man  

180 
60 
47 
22 
15 
14 

91 

9 
6 

1.6 
2.0 
3.5 
3.7 
4.9 
5.2 
7.0 
7.4 
14.4 

0.2 
0.4 
0.7 
0.78 
0.84 
0.80 
1.02 
1.33 
2.50 

0.03 
0.12 
0.16 
0.20 
0.25 
0.25 

0.05 
0.13 
0.20 
0.28 
0.29 
0.31 

Horse  

Cow  

Goat  

Sheep  

Pig  ... 

Cat  

Dog  

0.45 
0.89 

0.51 
0.99 

Rabbit  

280 


Agricultural  Chemistry 


The  composition  of  the  milk  of  a  single  species  is  by  no  means 
similar  to  that  of  another,  although  the  constituents  forming  it, 
so  far  as  they  have  been  investigated,  are  of  a  similar  nature. 

The  constituents  of  milk  may  be  divided  into  the  following 
classes :  water,  fats,  proteins,  sugar  and  ash.  The  water  of  milk 
constitutes  from  85  to  88  per  cent  and  needs  no  discussion. 

Fats  of  milk.  The  fats  resemble  in  chemical  constitution  the 
animal  and  vegetable  oils  and  fats  already  discussed;  that  is, 


The  milk  chambers  or  alveoli  of  an  udder;  A  and  B,  secreting  alveoli; 
C  and  D,  non-secreting  alveoli;  E,  alveolus,  which  has  discharged 
its  milk  (cells  appear  flattened). 

they  consist  of  compounds  of  fatty  acids  and  glycerine.  They 
differ  from  animal  fats  chiefly  in  containing  acid  radicals  of  low 
molecular  weight,  in  addition  to  the  heavy  acids,  such  as  oleic, 
•stearicj  and  palmitic,  which  are  the  principal  fatty  acids  in  the 
fats  of  animal  tissue.  Butter  fat  consists  of  the  glycerides  of 
>at  least  9  fatty  acids.  The  lowest  member  of  the  group  is  butyric 
acid,  the  highest  is  stearic  acid.  Oleic  acids  is  an  unsaturated 


Milk  and  Its  Products  281 

acid  and  belongs  to  another  series.     The  average  percentage  com- 
position of  milk  fat  is  about  as  follows : — 


Per  cent 
Butyrin,    CH  (CHO  ).  3.85 


3      5  x      4      728 


Caproin,  C  H  (C  H    OJ.   ..     3.60 


11      23 


Caprylin,  C  H  (C  H    O  ).  ..     0.55 


3      5         8      15     23 


Caprin,  CH  (C    H    OJ.    ..     1.90 


3      5         10      19     28 


Per  cent 
Myristin,  C  H  (C    H    O  )  ..   20.20 


3      5 


Palmitin,    C  H  (C    H    OJ..   25.70 


5         16      31     23 


Stearin,  C  H  (C,  H    OJ.  ..     1.80 


3      5         18      35     23 


Olein,  CH  (C    H    OJ.  ....   35.00 


3      5         18      33 


Laurin,  C3H5(C10H23O2)3   ..     7.40 

The  properties  of  these  fats  are  variable,  but  the  important 
fact  to  notice  is  the  occurrence  in  milk  fat  of  the  first  three  or 
four  fats  in  the  above  list,  but  mere  traces  of  which  are  present 
in  other  animal  fats.  Olein  and  the  first  four  members  of  the 
above  list  are  liquid  fats;  the  others  are  solid,  stearin  being  the 
hardest.  About  8.0  per  cent  of  the  fatty  acids,  chiefly  consisting 
of  the  first  three  in  the  series,  are  soluble  in  water.  The  soluble 
acids  have  a  low  boiling  point  and  can  be  separated  from  the  other 
fatty  acids  by  distillation.  These  facts  serve  to  distinguish  but- 
ter fat  from  animal  fats  such  as  tallow,  which  contains  but  traces 
of  soluble  and  volatile  fatty  acids.  Milk  fat,  however,  varies 
considerably  both  in  composition  and  physical  properties,  being 
affected  somewhat  by  feed,  period  of  lactation  and  other  circum- 
stances under  which  the  cows  are  kept. 

Fat  exists  in  milk  in  the  form  of  minute  globules,  varying  in 
diameter  from  .0016  to  .010  m.m.  In  the  milk  of  Jersey  and 
Guernsey  cows  the  average  size  of  the  globules  is  considerably 
larger  than  in  Hoist ein  milk;  also  in  the  milk  of  recently  calved 
cows  the  globules  are  larger  than  in  that  of  cows  far  advanced  in 
lactation.  This  fact  has  an  important  practical  bearing  upon 
the  speed  with  which  cream  rises.  The  milk  of  the  Jerseys  and 
Guernseys  throws  up  its  cream  very  rapidly,  while  from  the  milk 
of  the  Holstein  and  Ayrshire  breeds  the  cream  rises  relatively 
slower. 

The  proteins.  The  two  most  important  proteins  of  milk  are 
casein  and  albumin.  Traces  of  others  are  present,  but  they  are 
in  such  relatively  small  quantities  that  they  will  not  be  discussed 
here. 


282  Agricultural  Chemistry 

Casein  is  the  chief  protein  of  milk  and  exists  there  in  a  col- 
loidal state  and  not  in  perfect  solution.  It  can  be  separated  from 
the  milk  by  the  addition  of  an  acid  or  by  the  action  of  the  enzymer 
rennin,  which  is  contained  in  rennet.  In  the  souring  of  milkr 
during  which  process  acid  is  developed,  the  casein  is  precipitated. 
The  casein  formed  in  this  way  probably  consists  of  calcium-free 
casein,  for  it  is  generally  held  that  casein  exists  in  milk  in  com- 
bination with  calcium.  With  rennin,  however,  the  calcium-casein 
is  split  into  two  compounds,  para-casein  and  whey  protein.  The 
para-casein  in  the  presence  of  the  soluble  calcium  salts  of  the 
milk  precipitates  out,  while  the  whey  protein  remains  in  solution. 
In  the  absence  of  calcium  salts  rennin  will  not  curdle  milk.  This 
enzyme  acts  best  at  35°  C.  and  is  destroyed  at  70°  C.  It  is 
found  in  the  stomachs  of  all  mammals,  while  enzymes  possessing 
similar  properties  have  also  been  found  in  birds,  fishes,  many 
plants,  and  in  the  products  formed  by  the  action  of  certain  bac- 
teria. 

Mere  boiling  of  milk,  unless  continued  for  a  considerable  time, 
does  not  coagulate  the  casein.  Casein  is  the  only  protein  of 
cow's  milk  which  contains  phosphorus  in  its  molecule. 

Milk  albumin  differs  in  some  of  its  physical  properties  from 
blood  albumin.  It  is  in  complete  solution  in  milk  but  coagulates 
and  precipitates  when  heated  to  72°  C.  It  is  not  coagulated  by 
rennin  or  by  most  acids.  It  differs  from  casein  in  composition 
and  contains  about  twice  as  much  sulphur  and  no  phosphorus. 
In  colostrum  milk,  albumin  largely  predominates,  so  that  the  milk 
coagulates  on  heating. 

Milk  sugar,  C12H22O11.H2O.  The  sugar  contained  in  milk  is 
known  as  lactose.  It  occurs  in  the  milk  of  all  animals,  but  is  not 
present  in  plants,  and  consequently  does  not  exist  in  the  food  of 
the  dairy  cow.  It  is  prepared  by  evaporating  the  whey,  left 
after  cheese  making,  to  a  small  bulk,  from  which  lactose  will  cry- 
stallize out  in  large  crystals.  It  possesses  a  faint  sweet  taste, 
about  one-tenth  that  of  cane  sugar.  By  the  action  of  dilute  acids 


Milk  and  Its  Products 


283 


or  an  enzyme  known  as  lactase,  it  is  split  into  a  mixture  of 
dextrose  and  galactose: — 

C12H22011+II20=C6H1206+C6H120 
lactose  dextrose      galactose 

Milk  sugar  does  not  readily  undergo  alcoholic  fermentation,, 
but  is  readily  changed  into  lactic  acid  by  certain  micro-organ- 
isms. This  change  in  the  milk  sugar  is  the  cause  of  milk  souring. 
The  necessary  lactic  organisms  are  very  abundant  everywhere,, 
especially  in  the  vicinity  of  dairies  and  barns,  and  as  they  mul- 
tiply in  the  milk,  more  and  more  lactic  acid  is  formed.  Sweet 
milk  has  an  acidity  of  from  0.12  to  0.20  per  cent,  expressed  as 
lactic  acid.  When  about  0.40  per  cent  is  present,  the  milk  ac- 
quires a  sour  taste,  and  when  the  amount  reaches  0.6  to  0.7  per 
cent,  curdling  commences.  "With  certain  organisms,  the  amount 
of  lactic  acid  may  reach  from  2.0  to  3.0  per  cent,  but  ordinarily 
it  does  not  exceed  0.9  per  cent. 

The  ash  of  milk.  When  water  is  removed  from  milk  by  evap- 
oration and  the  residue  then  burned,  a  white  ash  is  always  left 
behind.  This  consists  of  the  mineral  matter  and  salts  of  the 
milk,  together  with  sulphates,  phosphates  and  carbonates  pro- 
duced by  the  burning  of  the  organic  matter  of  the  milk.  It 
amounts  in  cow's  milk  to  about  0.7  per  cent,  and  consists  of: — 


Per  cent 

Potash    22     to  27 

Soda 10    to  12 

Lime 19     to  24 

Magnesia    1.8  to    3 


Per  cent 

Ferric   oxide    traces  to    0.2 

Sulphur  trioxide 3.8  to    4.4 

Phosphoric  acid 22     to  27 

Chlorine    .  13     to  16 


Milk  also  contains  traces  of  citric  acid.  This  is  not  free,  but 
in  combination  with  bases  as  citrates  and  amounts  to  about  0.1 
per  cent  of  the  milk. 

The  gases  of  fresh  milk  are  chiefly  carbon  dioxide,  oxygen  and 
nitrogen.  These  amount  to  about  85  c.  c.  per  liter,  the  carbon 
dioxide  constituting  approximately  90  per  cent  of  the  total  gas. 
On  standing,  or  even  during  the  process  of  milking,  there  is  a 
rapid  exchange  of  gases,  the  carbon  dioxide  greatly  diminishing, 


284  Agricultural  Chemistry 

while  the  oxygen  and  nitrogen  rapidly  increase.  This  increase 
in  oxygen  and  nitrogen  is  really  an  absorption  of  air  and  em- 
phasizes the  necessity  of  maintaining  a  pure,  sweet  atmosphere, 
to  which  fresh  milk  is  to  be  exposed. 

Physical  properties.  Milk  is  a  white,  or  yellowish  white, 
opaque  fluid,  with  a  sweet  taste.  The  specific  gravity  varies  usu- 
ally from  1.027  to  1.034.  The  solids  other  than  fat  tend  to  raise 
the  specific  gravity,  while  the  fat  tends  to  lower  it.  As  cream 
may  be  removed  and  water  added  without  altering  the  specific 
gravity,  no  safe  conclusion  as  to  the  quality  of  the  milk  can  be 
based  on  this  test  alone.  When  fresh  milk  is  quickly  cooled  and 
its  specific  gravity  taken  at  once,  and  then  again  after  some  hours 
and  at  the  same  temperature,  a  small  but  decided  rise  in  density 
is  observable,  usually  amounting  to  about  0.0005.  This  is  known 
as  Eechnagel's  phenomenon,  and  has  been  explained  in  several 
ways.  It  has  been  ascribed  to  the  escape  of  gases  from  the  milk ; 
to  a  change  in  the  mechanical  condition  of  fhe  casein;  and  lastly 
to  the  solidfication  of  the  fat  globules.  It  is  suggested  that 
quick  cooling  does  not  immediately  solidify  the  fat  globules, 
which  are  liquid  at  the  temperature  of  the  cow,  but  that  they  re- 
main in  a  super-cooled  liquid  state.  As  they  slowly  solidify,  they 
contract,  thereby  increasing  the  density  and  raising  the  specific 
gravity. 

Chemical  composition.  This  varies  considerably  according 
to  breedj  individuality,  age,  period  of  lactation  and  food.  The 
mean  composition,  according  to  many  American  analyses,  is  as 
follows : — 


Per  cent 

Water    87.1 

Fat  3.9 

Sugar  5.1 


Per  cent 

Casein   2.5 

Albumin   0.7 

Ash    .  0.7 


It  must  be  remembered  that  these  figures,  being  averages,  im- 
ply the  existence  of  many  values  either  above  or  below  those 
given.  As  a  rule  the  fat  is  most  liable  to  variation.  The  fac- 
tors influencing  the  composition  of  milk  will  be  briefly  discussed 
under  the  following  heads : — 


Milk  and  Its  Products 


285 


Breed.  It  is  well  known  that  breed  is  a  very  important  factor 
in  influencing  the  composition  of  milk.  The  following  table  gives 
the  average  composition  of  the  milk  from  several  individuals  of 
the  breed  represented.  Individual  variations  from  the  figures 
given  are  of  course  to  be  found,  and  the  figures  only  represent 
the  general  trend  of  the  breed. 

Composition  of  Milk  of  Different  Breeds 


Name  of  breed 

Solids 

Fat 

Casein 

Albumin 

Holatein     p  

Per  cent 
11.80 

Per  cent 
3/26 

Per  cent 
2.20 

Per  cent 
.64 

Ayrshire  

12.75 

3.76 

2.46 

.61 

Shorthorn  

14.30 

4.28 

2.79 

.64 

Devon  

14.50 

4  89 

3.10 

.83 

Gueuusey  

14.90 

5  38 

2.91 

.65 

Jersey  

15.40 

5.78 

3.03 

.65 

Individuality.  It  is  uncommon  to  find  in  a  herd  of  cows  of 
the  same  breed  any  two  individuals  whose  milk  is  of  the  same 
composition.  This  is  true  whether  we  consider  single  milkings 
or  the  average  of  many. 

Age.  So  far  as  there  are  published  data  on  the  influence  of 
the  age  of  cows  on  the  composition  of  milk,  they  indicate  a  ten- 
dency for  the  heifer  to  show  a  slightly  higher  fat  content  than 
the  mature  cow.  Individual  exceptions,  however,  are  not  infre- 
quent, and  more  data  are  needed  to  settle  the  question. 

Period  of  lactation.  Immediately  after  calving,  the  first 
product  of  the  udder  is  colostrum.  This  is  a  yellow  liquid,  of 
strong,  pungent  taste,  and  very  different  from  normal  milk.  It 
is  characterized  by  containing  small  clusters  of  cells,  known  as 
colostrum  granules  and  is  very  rich  in  albumin.  This  may 
reach  13.5  per  cent.  Because  of  the  high  content  of  albumin, 
colostrum  milk  sets  to  a  solid  mass  on  heating.  This  test  serves 
to  distinguish  it  from  normal  milk.  This  first  milk  is  exceed- 
ingly important  to  the  young  animal  at  birth,  and  serves  to 


286 


Agricultural  Chemistry 


cleanse  the  alimentary  tract  and  properly  start  the  work  of  di- 
gestion. After  eight  to  ten  days  from  calving  the  secretion  be- 
comes like  normal  milk,  but  the  colostrum  cells  can  usually  be 
found  in  the  milk  for  about  14  days  after  calving. 

The  milk  during  the  first  month  after  calving  is  generally  rich 
in  fat  and  total  solids,  and  these  diminish  during  the  second 
month.  After  the  second  or  third  month,  the  fat  and  protein,  aa 
well  as  the  sugar,  continue  to  increase  from  month  to  month  dur- 
ing the  entire  period  of  lactation.  The  following  table,  taken 
from  the  data  of  the  New  York  State  Station,  represents  the 
monthly  averages  of  nearly  100  different  lactation  periods. 

Influence  of  Lactation  on  the  Composition  of  Milk 


Month  of  lactation 

Fat 

Proteins 

Casein 

Albumin 

1  

Per  cent 
4.30 

Per  cent 
3.16 

Per  cent 
2.54 

Per  cent 
0.62 

2  

4.11 

2.99 

2.42 

0.57 

3  

4.21 

3.04 

2.46 

0.58 

4  

4.25 

3.13 

2.52 

0.6-1 

5  

4.38 

3.25 

2.61 

0.64 

6  

4.53 

3.36 

2.68 

0.65 

7  

4.57 

3.40 

2.74 

0.66 

8  

4.59 

3.47 

2.80 

0.67 

9  

4.67 

3.57 

2.90 

0.67 

10  

4.90 

3.79 

3.01 

0.78 

11  

5.07 

4.04 

3  13 

0.91 

Occasionally  individuals  may  depart  from  the  general  ten- 
dency shown  in  the  above  table,  but  usually  they  conform  to  the 
general  rule  which  the  table  indicates.  The  average  size  of  the 
fat  globules  diminishes  with  advancing  lactation,  but  their  num- 
ber per  unit  volume  increases. 

Feed.  The  influence  of  the  feed  of  cows  upon  the  composition 
of  their  milk  is  a  matter  upon  which  many  varied  opinions  are 
held.  There  is  a  widespread  belief  that  this  influence  is  con- 
siderable, but  all  experimental  evidence  shows  it  to  be  very  small. 


Milk  and  Its  Products  287 

Under  scanty  food  supply  the  quality  and  especially  the  quantity 
of  milk  may  be  considerably  reduced.  This  is  evidenced  by  the 
results  secured  at  the  Cornell  Station  with  a  poorly  fed  herd  and 
again  when  the  same  herd  was  liberally  fed.  Under  those  con- 
ditions, where  a  liberal  supply  of  nutrients  wras  given,  the  flow 
of  milk  was  nearly  doubled  and  the  percentage  of  fat  slightly 
increased.  Again,  there  appears  to  be  some  distinct  evidence 
that  a  change  from  a  ration  with  a  wide  nutritive  ratio  to  one 
with  a  narrow  ratio,  is  for  a  time,  attended  with  a  production 
of  milk  slightly  richer  in  fat;  but  the  change  is  only  transient, 
and  even  if  the  food  with  a  high  protein  ration  be  continued,  the 
milk,  after  allowance  is  made  for  the  effect  of  advancing  lacta- 
tion, shows  a  tendency  to  return  to  its  previous  composition. 

In  any  case,  it  appears  that,  provided  cows  are  sufficiently  fed, 
change  of  feed  has  very  little  permanent  effect  upon  the  com- 
position of  their  milk.  Violent  and  sudden  changes  in  the  char- 
acter of  their  feed  may  cause  a  sudden  fluctuation  in  the  com- 
position of  the  milk,  but  after  a  short  period  it  will  tend  to  re- 
turn to  a  composition  characteristic  for  that  animal. 

The  opinion  that  it  is  possible  to  feed  fat  into  milk  has  widely 
prevailed,  but  such  a  notion  is  based  upon  a  misconception  of 
how  milk  is  formed.  "When,  however,  we  remember  that  the  cells 
of  the  mammary  gland  are  selective  in  function,  and  that  with 
the  same  feeds  a  Jersey  cow  always  makes  Jersey  milk,  and  a 
Holstein  cow  Holstein  milk,  then  the  many  failures  to  feed  fat 
into  milk  become  intelligible.  The  careful  and  well  planned 
work  of  Lindsey,  in  which  a  number  of  vegetable  oils  have  been 
added  to  a  basal  ration,  gave  in  some  cases  slight  but  only  tem- 
porary increases  of  fat  in  the  milk,  while  with  other  oils  no  in- 
crease whatever  was  noticed. 

Certain  feeds,  however,  affect  the  character  of  the  fat  in  the 
milk,  which  is  manifested  by  a  change  in  the  hardness  and  physi- 
cal properties  of  the  butter  produced.  It  is  agreed  that  cotton- 
seed meal  has  the  effect  of  raising  the  melting  point  &f  butter, 
while  gluten  feed,  rich  in  oil,  produces  a  softer  butter  of  lower 


288  Agricultural  Chemistry 

melting  point.  In  experiments  at  the  Wisconsin  Station,  long 
continued  feeding  of  nutrients  entirely  from  the  corn  plant,  as 
well  as  from  the  wheat  plant,  tended  to  produce  soft,  low-melting 
milk  fats,  while  the  nutrients  from  the  oat  plant  produced  fats 
making  a  hard  butter,  with  a  high  melting  point. 

Season.  The  influence  of  season  upon  the  composition  of  milk, 
apart  from  the  effect  of  advancing  lactation,  is  largely  associated 
with  the  food  supply.  "When  this  is  normally  maintained  and 
the  animals  are  protected  from  the  effect  of  weather  changes, 
variations  in  the  composition  of  the  milk  appear  to  be  slight. 

Time  and  intervals  between  milking.  "Where  the  time  be- 
tween milkings  is  the  same  and  there  are  no  other  disturbing  in- 
fluences, the  composition  of  morning's  and  evening's  milk  shows 
practically  no  difference.  Where  the  intervals  are  unequal,  there 
may  be  a  considerable  variation  in  the  two  milkings.  In  an  ex- 
periment where  17  Shorthorn  cows  were  milked  at  6  a.  m.  and 
3  p.  m.  the  average  per  cent  of  fat  in  the  morning's  milk  was 
3.2,  and  4.5  per  cent  in  the  evening's  milk. 

It  is  well  known  that  the  first  milk  drawn  from  the  udder  at 
milking  time  is  very  low  in  fat,  sometimes  being  as  low  as  1  per 
cent,  while  the  last  portion  may  contain  as  high  as  10  per  cent. 
In  these  two  fractions,  however,  the  other  constituents  are  in 
about  the  same  proportion  as  would  be  found  in  the  entire  milk- 
ing. 

Milk  of  other  animals.  The  following  table  compiled  from 
several  sources,  gives  the  average  composition  of  the  milk  of 
other  animals;  some  of  the  results  are  probably  not  truly  rep- 
resentative, due  to  improper  sampling. 

There  is  a  considerable  difference  in  the  behavior  of  the  casein 
of  the  milk  of  different  animals  when  treated  with  rennet.  With 
cow's  milk  the  enzyme  of  rennet,  rennin,  gives  a  coherent,  curdy 
precipitate,  while  with  human  milk  the  coagulum  is  much  more 
finely  divided.  To  this  fact  has  been  attributed,  in  part,  the 
non-adaptability  of  cow's  milk  to  infant  feeding.  It  will  also 
be  noticed  that  cow's  milk  differs  from  the  natural  .food  of  the 


Milk  and  Its  Products 


289 


human  infant  in  containing  more  ash  and  proteins  and  much  less 
sugar.  It  is  upon  these  chemical  facts  that  the  modification  of 
cow's  milk,  by  dilution  and  addition  of  lactose,  rendering  it  suit- 
able for  infant  feeding,  is  based.  However,  experience  is  teach- 
ing that  in  most  cases  the  whole  milk  of  the  cow,  without  dilution, 
can  be  safely  used  for  infant  feeding.  There  is  a  growing  belief, 
though,  that  it  must  not  be  too  rich  in  fat. 

Preservation  of  milk.     Normal  milk  as  it  occurs  in  the  cow's 
udder  usually  contains  relatively  few  organisms;  but  in  the 


Composition  of  Milks 


Animal 

Fat 

Casein 

Sugar 

Ash 

Solids 
not  fat 

Woman  

Per  cent 
3.3 
1.0 
6.5 
5.3 
1.7 
4.6 
2.9 
4.5 
9.6 
3.3 
10.5 
19.6 
48.5 
43.7 

Per  cent 
1.5 
1.1 
4.3 
7.1 
2.2 
7.2 
3.8 
Trace 
9.9 
9.5 
15.5 
3.1 
11.2 
7.1 

Per  cent 
6.8 
5.5 
5.0 
4.2 
6.0 
3.1 
5.7 
4.4 
3.2 
4.9 
2.0 
8.8 
1.3 

Per  cent 
0.2 
0.4 
0.7 
0.8 
0.4 
0.8 
0.6 
0.1 
1.3 
1.0 
2.5 
0.6 
0.5 
0.4 

Per  cent 
8.5 
7.8 
10.2 
12.4 
8.6 
11.4 
10.2 
4.5 
13.8 
15.0 
20.1 
12.6 
13.1 
7.7 

Ass  

Goat  

Ewe  

Mare  

Sow  

Camel  

Hippopotamus  

Bitch  

Cat  

Rabbit  

Elephant  

Porpoise  

Uhale  

operation  of  milking  and  during  subsequent  exposure  to  the  air, 
bacteria,  molds  and  yeasts  find  admission.  They  may  find  their 
way  into  the  milk  from  the  hands  of  the  milker,  the  teats  and 
hair  of  the  cow,  and  often  from  the  vessel  in  which  the  milk  is 
collected.  The  ordinary  souring  of  milk  is  produced  by  various 
species  of  bacteria,  which  during  their  growth  convert  the  milk- 
sugar  into  lactic  acid.  This  formation  of  acid  induces  the  curd- 
ling of  the  milk.  This  generally  occurs  when  the  amount  of  acid 


290  Agricultural  Chemistry 

reaches  about  0.7  per  cent.  Curdling  is  produced  by  less  acid  if 
the  milk  is  heated. 

Other  organisms,  and  often  of  a  more  dangerous  character, 
sometimes  find  their  way  into  milk.  Outbreaks  of  diarrhoea,  ty- 
phoid and  cholera  have  been  traced  to  contaminated  milk.  It  has 
also  been  shown  that  milk  can  act  as  a  carrier  of  tuberculosis. 
Milk,  too,  has  the  property  of  absorbing  gases  and  vapors  and  in 
consequence  readily  acquires  odors  and  flavors  from  the  air. 

All  these  facts  emphasize  the  necessity  of  cleanliness  in  milk 
production  and  precautionary  measures  to  check  bacterial  devel- 
opment should  the  milk  become  seeded.  Their  growth  can  be 
checked  by  cooling  the  milk  as  soon  as  it  is  produced.  This  pre- 
vents a  rapid  development  of  the  organisms  already  in  the  milk, 
but  will  not  entirely  prevent  their  development.  It  will  prolong 
the  sweetness  of  the  milk.  In  order  to  destroy  the  organisms 
which  have  gained  access  to  the  milk,  heating  or  the  use  of  anti- 
septics must  be  resorted  to.  "Where  the  process  of  heating  is  car- 
ried on  at  a  temperature  high  enough  to  completely  destroy  all 
organisms  and  their  spores — a  process  known  as  sterilization 
and  requiring  a  temperature  above  100°  C. — undesirable  chem- 
ical changes  are  produced  in  the  milk.  The  sugar  is  turned 
brown,  the  albumin  partly  precipitated,  and  the  milk  acquires  a 
burnt  or  cooked  flavor.  To  avoid  these  disadvantages  the  process 
known  as  Pasteurization  is  often  substituted.  The  milk  is  heated 
to  only  60  to  80°  C.,  whereby  the  flavor  is  little  affected  and  most 
of  the  active  bacteria  are  killed.  The  keeping  qualities' are  thus 
materially  increased. 

Antiseptics.  By  adding  various  substances  to  milk,  the  growth 
of  micro-organisms  can  be  impeded,  if  not  entirely  prevented. 
When,  however,  such  quantities  of  an  antiseptic  are  added  as 
will  prevent  bacterial  growth,  then  there  is  little  doubt  that  the 
milk  is  made  unsuitable  for  human  consumption.  The  chief 
preservatives  in  common  use  are  boric  acid,  H3B03,  salicylic  acid, 
C6H4OHCOOH,  formaldehyde,  CH20  and  benzoic  acid,  C6H5- 
COOH.  Their  use  in  any  quantity  is  reprehensible,  allowing 


Milk  and  Its  Products  291 

uncleanly  methods  in  milk  production  to  be  practiced,  as  well  as 
endangering  the  health  of  the  consumer,  and  should  be  absolutely 
prevented. 

Products  derived  from  milk.  Cream.  The  fat  of  milk  exists 
in  globules  and  is  specifically  lighter  than  the  aqueous  portion  of 
the  milk.  This  makes  the  globules  tend  to  rise  to  the  surface, 
where  they  form  a  layer  of  cream.  The  specific  gravity  of  fat 
at  15°  C.  is  .930,  while  the  serum  in  which  the  globules  float  has 
a  specific  gravity  of  about  1.036.  The  globules  are  of  various 
sizes.  They  are  considerably  larger  in  the  milk  of  the  Jersey  and 
Guernsey  breeds  than  in  the  Ayrshire  and  Holstein  breeds.  The 
Devons  and  Shorthorns  hold  an  intermediate  position.  The 
smaller  the  globule,  the  larger  is  its  surface  in  proportion  to  its 
volume,  and  the  greater  the  resistance  to  its  rise.  For  this  reason 
Jersey  milk  creams  easier  than  that  from  breeds  with  smaller 
globules. 

Cream  can  be  separated  from  milk  by  gravitation  or  by  sub- 
stituting for  gravity  the  much  greater  force  produced  by  rapid 
rotation.  When  milk  leaves  the  cow  it  will  have  a  temperature 
of  about  90°  F.,  and  where  set  for  cream  should  be  cooled  as 
quickly  as  possible.  There  are  two  methods  in  use  for  the  separ- 
ation of  cream  by  the  gravity  processes,  namely,  shallow  setting 
and  deep  setting.  In  the  former  the  milk  is  placed  in  shallow 
vessels  to  a  depth  of  2  to  4  inches,  cooled  to  about  60°  F.  and 
kept  at  that  temperature  for  24  or  36  hours.  The  cream  layer 
is  then  removed  by  a  shallow  spoonlike  vessel,  or  sometimes  by 
running  off  the  milk  into  another  vessel  through  a  hole  at  the 
bottom  of  the  creaming  pan.  Under  these  conditions  of  cream- 
ing a  large  surface  is  exposed,  the  milk  may  receive  a  great  num- 
ber of  bacteria,  and  decomposition  of  a  part  of  the  protein  and 
sugar  may  rapidly  take  place.  The  cream  obtained  in  this  way 
is  liable  to  be  contaminated  with  various  strongly  flavored  prod- 
ucts of  decomposition,  resulting  in  a  poor  quality  of  bu'ter.  The 
process  is  not  efficient,  as  only  about  80  per  cent  of  the  m^k  fat 
is  removed. 


292  Agricultural  Chemistry 

By  the  deep-setting  system,  the  milk,  while  still  warm,  is  placed 
in  cylindrical  vessels,  usually  about  8  to  12  inches  in  diameter 
and  15  to  20  inches  deep,  which  are  then  immersed  in  ice-cold 
water.  The  cream  rises  quickly  and  the  process  will  be  prac- 
tically complete  in  12  hours.  By  this  process  90  to  95  per  cent 
of  the  fat  can  ~be  removed,  dependent  upon  conditions  of  cooling, 
manipulation,  and  the  breed  of  the  cow.  It  has  been  found  that 
by  this  process  twice  as  much  fat  remains  in  the  skim  milk  from 
Holstein  cows  as  in  that  from  Guernseys  and  Jerseys,  owing  to 
the  slower  rising  of  the  small  fat  globules  in  Holstein  milk. 

Many  explanations  of  the  efficiency  of  this  system  have  been 
attempted.  Since  fat  expands  and  contracts  with  changes  of 
temperature  more  rapidly  than  does  water,  the  effect  of  cooling 
upon  milk  would  be  to  lessen  the  difference  in  specific  gravity 
between  fat  and  water ;  it  would  also  increase  the  viscosity  of  the 
milk,  both  conditions  working  against  a  rapid  rise  of  the  fat 
globules.  Perhaps  the  most  satisfactory  explanation  is  the  one 
given  by  Doctor  Babcock.  There  exists  in  milk  a  substance  sim- 
ilar in  character  to  blood  fibrin,  which,  when  formed  produces 
more  or  less  of  a  network  throughout  the  body  of  the  milk.  By 
rapidly  cooling  the  milk;  the  formation  of  fibrin  threads  is 
checked.  This  allows  the  fat  globules  a  free  path  of  movement, 
with  the  resultant  rapid  formation  of  the  cream  layer.  The  ex- 
istence of  fibrin  in  milk  has  been  definitely  proven. 

Separators.  A  third  plan  of  separating  cream  is  by  subject- 
ing the  milk  to  extremely  rapid  horizontal  revolution  in  a  cen- 
trifugal machine.  Under  this  condition  the  serum,  being  the 
constituent  of  heaviest  specific  gravity,  is  thrown  to  the  outer 
side  of  the  revolving  vessel  while  the  fat  globules  rise  into  the 
center  of  the  mass.  The  milk  should  be  warmed  to  about  85°  F. 
previous  to  separating,  for  the  purpose  of  lowering  its  viscosity. 
By  providing  suitable  outlets,  the  skim  milk  can  be  directed  into 
one  channel  and  the  cream  into  another.  By  adjusting  the  size 
of  one  of  these  openings,  thick  or  thin  cream  can  be  obtained  at 
will.  Both  the  cream  and  skim  milk  thus  obtained,  are,  of  course, 


Milk  and  Its  Products 


293 


perfectly  sweet  The  separation  of  the  fat  is  far  more  complete 
than  by  either  of  the  other  processes,  from  97  to  98  per  cent  be- 
ing recovered  in  a  good  machine. 

Composition.  Cream  varies  enormously  in  composition,  the 
proportion  of  fat  varying  from  as  low  as  10  per  cent  to  as  high 
as  60  or  70  per  cent.  By  shallow  setting,  a  product  containing 
from  15  to  40  per  cent  is  usually  obtained ;  at  low  temperatures 
about  20  per  cent  of  fat  is  usually  present.  In  the  deep-setting 
process  the  cream  obtained  will  contain  about  20  to  25  per  cent 
of  fat.  Cre^am  separated  by  the  centrifugal  process  will  vary 
according  to  the  mode  of  working.  It  may  be  quite  poor,  or  it 
may  contain  50  to  60  per  cent.  Generally  speaking,  thin  cream 
will  contain  15  to  25  per  cent  of  fat,  and  thick  cream  30  to  50 
per  cent  of  fat. 

Devonshire-" clotted  cream"  is  prepared  by  setting  the  milk 
in  shallow  pans  and  at  a  fairly  cool  temperature  for  12  hours. 
It  is  then  heated  to  a  temperature  of  70  to  80°  C.  until  the  sur- 
face becomes  sharply  wrinkled.  It  is  then  set  in  the  cold  for  12 
hours  and  skimmed.  Such  clotted  cream  usually  contains  about 
58  per  cent  of  fat,  34  per  cent  of  water  and  about  8  per  cent  of 
solids  not  fat. 

Skimmed  milk  varies  in  composition  according  to  the  more  or 
less  complete  removal  of  the  fat.  Milk  thoroughly  skimmed  after 
shallow  setting  will  contain  about  1  per  cent  of  fat.  "With  deep 
setting  and  ice,  the  per  cent  of  fat  left  in  the  milk  will  vary  from 
0.15  to  0.40.  When  the  centrifugal  machine  has  been  used  the 
percentage  will  be  from  .05  to  .15.  Milk  of  average  quality  may 
be  expected  to  yield  with  a  good  centrifugal  machine,  skimmed 
milk  of  about  the  following  composition: — 


Per  cent 

"Water    90.54 

Fat 0.10 

Sugar 4.94 


Per  cent 

Casein    3.11 

Albumin  0.42 

Ash.  etc.  .  0.89 


Skimmed  milk  contains  a  valuable  amount  of  food  stuffs,  and 
should  be  utilized  on  the  farm  for  feeding  pigs  or  in  other  ways. 


294  Agricultural  Chemistry 

Though  poorer  in  fat,  machine  separated  milk  has  the  advantage 
of  being  sweet  and  of  keeping  better  than  the  product  from  other 
processes  of  skimming. 

Butter.  "When  cream  or  milk  is  agitated  for  some  time,  the 
fat  globules  coalesce  and  butter  separates  out  in  irregular  masses. 
While  these  masses  are  not  continuous  fat,  very  few  of  the  origi- 
nal globules  remain.  The  spherical  globules  visible  in  butter 
under  the  microscope  consist  of  minute  drops  of  butter-milk  or 
water,  enclosed  in  the  fat. 

Churning  is  a  mechanical  process.  The  fat  globules  collide, 
adhere,  and  the  large  irregular  masses  thus  formed  become  cen- 
ters of  growth,  to  which  other  fat  globules  adhere.  Portions  of 
the  aqueous  liquid,  butter-milk,  are  enclosed  in  the  masses  of  fat. 
During  the  "working"  of  the  butter,  the  butter-milk  is  partly 
pressed  out.  For  butter  to  be  of  good  quality,  it  must  possess  a 
certain  texture  and  grain  and  be  neither  hard  nor  greasy.  This 
desirable  result  can  only  be  attained  by  careful  churning  at  a 
favorable  temperature.  If  the  temperature  of  the  cream  is  too 
low  the  butter  will  be  long  in  coming  and  will  be  hard  in  texture. 
If  the  temperature  is  too  high,  the  butter  will  come  very  speedily, 
but  the  product  will  be  greasy  and  destitute  of  grain.  No  tem- 
perature can  be  fixed  as  the  best  at  which  churning  should  always 
take  place.  The  proportion  of  solid  and  liquid  fats  in  the  milk 
varies  somewhat  with  the  breed  and  feed  of  the  cow,  and  this 
necessitates  a  change  in  the  temperature.  From  45  to  65°  F.  is 
the  greatest  range  usually  employed  and  in  most  cases  from  50  to 
60°  F.  is  chosen.  Ripened  or  sour  cream  must  be  churned  at  a 
higher  temperature  than  that  required  for  sweet  cream.  The 
exact  temperature  most  suitable  for  churning  may  be  ascertained, 
by  recording  every  day  the  temperature  employed,  the  length  of 
time  occupied  in  churning  and  the  character  of  the  product. 
"When  this  is  done  the  experience  gained  can  be  used  in  selecting 
the  most  suitable  temperature. 

The  temperature  may  rise  during  churning,  work  being  con- 
verted into  heat.  This  causes  an  expansion  of  the  air  in  the 


Milk  and  Its  Products  295 

churn.  In  addition,  the  carbon-dioxide  in  solution  in  the  serum 
of  a  ripened  cream  is  driven  out  by  the  agitation.  These  two  fac- 
tors give  rise  to  the  pressure  observed  within  the  churn.  Churn- 
ing should  always  be  stopped  as  soon  as  the  butter  appears  in 
fine  grains.  This  allows  a  more  complete  separation,  by  washing, 
of  the  butter-milk,  and  removes  one  of  the  important  factors  in 
the  production  of  mottles  in  butter.  Further,  the  more  com- 
pletely the  butter-milk  is  removed,  the  better  will  be  the  keeping 
qualities  of  the  butter. 

Freshly  separated  cream  is  sometimes  churned,  but  it  is  gen- 
erally admitted  that  the  best  flavor  and  aroma  for  butter  can  only 
be  obtained  by  the  use  of  properly  ripened  cream.  This  is  cream 
to  which  lactic  acid  organisms  have  either  gained  access  spon- 
taneously, or,  as  is  preferred  in  modern  practice,  have  been  added 
in  the  form  of  a  starter  of  sour  skimmed  milk  or  some  pure  cul- 
ture of  the  lactic  organisms.  The  degree  of  ripeness  which  is 
probably  best,  corresponds  to  about  0.5  per  cent  of  lactic  acid; 
but  the  acidity  most  suitable  depends  to  some  extent  upon  the 
flavor  desired  in  the  butter.  If  the  cream  is  over  ripe,  the  casein 
present  may  be  hardened  and  on  churning  is  found  as  white 
specks  or  flakes  in  the  butter,  spoiling  its  appearance  and  endan- 
gering its  keeping  qualities. 

Salt  is  usually  added  to  butter,  serving  both  as  a  condiment 
and  as  preservative,  the  proportion  varying  from  a  mere  trace 
to  5  or  6  per  cent. 

Composition  of  butter.  The  main  constituent  is  of  course  fat, 
but  in  addition,  water,  casein,  milk  sugar  and  ash  are  also  pres- 
ent. The  amount  of  fat  is  usually  about  80  to  86  per  cent,  water 
about  11  to  12,  casein  from  0.6  to  1.5  and  salt  from  0.1  to  4.0  per 
cent.  Under  the  present  pure  food  law  of  the  United  States  it  is 
unlawful  to  sell  butter  containing  more  than  16  per  cent  of  water. 
So  called  "milk-blended  butters"  prepared  by  kneading  butter 
in  milk,  usually  contain  an  excessive  quantity  of  water  and  a  High 
proportion  of  casein. 

Renovated  butter.     In  this  country  old  and  rancid  butter  is 


296  Agricultural  Chemistry 

sometimes  converted  into  what  is  known  as  renovated,  process, 
or  aerated  butter.  This  is  done  by  melting  the  butter,  separat- 
ing the  fat  from  the  casein,  water,  etc.,  blowing  air  through  the 
fat  to  remove  the  unpleasant  odors,  and  then  churning  the  liquid 
fat  with  milk  until  an  emulsion  is  formed.  This  is  then  quickly 
cooled  in  ice  and  a  granular  mass  results.  It  is  then  worked, 
salted,  and  made  up  as  butter. 

Oleomargarine  is  also  known  as  margarine  or  butterine.  This 
product,  which  is  intended  as  a  substitute  for  butter,  is  made  by 
churning  so  called  oleo  oil  with  lard,  milk,  sometimes  a  little  but- 
ter, and  occasionally  cotton-seed  oil  or  peanut  oil,  in  a  warm 
state.  After  the  churning  the  mixture  is  quickly  cooled,  salted 
and  "worked."  Where  coloring  matters  are  used,  with  the  in- 
tention of  imitating  butter,  a  tax  of  10  cents  a  pound  is  imposed. 
On  uncolored  ' '  oleo ' '  a  tax  of  %  cent  per  pound  is  levied. 

The  oleo  oil  is  made  from  beef  fat  by  melting,  carefully 
clarifying,  and  allowing  it  to  stand  at. a  temperature  of  about 
30°  C.  The  semi-solid  mass  which  results  is  then  separated  ~by  a 
press  into  solid  stearin  and  a  liquid  composed  of  olein  and  pal- 
mitin. 

Pure  butter  can  be  distinguished  from  ' '  renovated ' '  butter  and 
from  "oleo"  by  its  behavior  when  heated  in  a  test  tube  or  spoon 
over  a  flame.  Oleomargarine  and  renovated  butter  boil  with 
much  sputtering  and  produce  no  foam,  or  very  little,  while  gen- 
uine butter  in  boiling  produces  more  foam  and  less  noise. 

Butter-milk.  The  liquid  remaining  in  the  churn  after  the 
separation  of  butter  from  the  cream  varies  a  good  deal  in  com- 
position. "With  good  churning  of  ripened  cream,  the  percentage 
of  fat  in  the  butter-milk  may  be  0.3  or  less.  When  sweet  cream 
is  churned  1.0  per  cent  of  fat  may  be  expected.  The  average 
composition  of  butter-milk  will  be  about  as  follows: — Water, 
90.9  per  cent;  proteins,  3.5;  fat,  0.5;  sugar  and  lactic  acid,  4.4; 
ash,'  0.7.  The  chief  use  for  butter-milk  has  been  as  food  for  pigs, 
but  there  is  a  growing  demand  for  it  as  human  food.  The  finely 
divided  condition  of  its  protein  makes  it  readily  and  easily  di- 


Milk  and  Its  Products 


297 


gestible.  The  preparation  of  a  new  product,  butter-milk  cream, 
will  probably  increase  the  consumption  of  this  material  as  human 
food.  This  product  is  prepared  by  holding  the  butter-milk  at  75 
to  78°  F.  for  about  2  hours,  and  finally  heating  to  130  to  140°  F. 
for  a  short  time.  This  treatment  induces  an  aggregation  of  the 
finely  divided  protein,  allowing  the  material  to  be  strained  and 
collected,  which  otherwise  could  not  be  done. 

The  following  table  shows  how  the  various  constituents  of  100 
pounds  of  milk  are  distributed  when  the  milk  is  creamed  and 
made  into  butter : — 

Distribution  of  Milk  Solids  in  Butter  Making 


Products  from  100  Ibs.  ofnnlk  in  Ibs. 

100  Ibs. 
oi  milk 

20  Ibs. 
of  cream 

Skimmed 
milk 

Butter 

Butter 
milk 

Total  solids  

13.00 
4.00 
3.50 
4.75 
0.75 

5.18 
3.88 
0.50 
0.75 
0.05 

7.82 
0.12 
3.00 
4.00 
0.70 

4.00 
3.83 
0.10 
0.05 

1.18 

0.05 
0.40 
0.70 
0.03 

Fat  

Casein  and  albumin 
Sugar  and  acid  
Ash  

The  4  pounds  of  solid  matter  recovered  in  the  butter,  which 
contains  3.83  pounds  of  fat,  together  with  the  salt  and  water  pres- 
ent, make  about  4.6  pounds  of  marketable  butter. 

Condensed  milk  and  milk  powders.  Condensed  milk  is  pre- 
pared by  evaporating  milk  in  vacuum  pans  until  its  volume  is 
reduced  to  about  one-third  or  one-fourth  of  the  original,  and  then 
sealing  the  condensed  product  while  hot.  In  many  brands  cane 
sugar  is  added  in  large  proportion.  This  aids  in  preserving  the 
product,  even  after  the  cans  are  opened.  To  other  brands,  often 
known  as  evaporated  cream,  no  sugar  is  added. 

The  composition  of  these  products  varies,  the  fat  being  liable 


298  Agricultural  Chemistry 

to  considerable  variation.     The  following  analysis  may  be  taken 
as  typical : — 

Sweetened  Unsweetened 

Per  cent  Per  cent 

Water    25.7  71.7 

Fat  10.7  8.1 

Protein 8.5  8.7 

Milk  sugar  11.9  9.9 

Cane  sugar 41.9  .... 

Ash  1.3  1.6 

Milk  powders  are  made  by  several  processes.  One  of  the  earli- 
est was  to  evaporate  the  milk  in  a  thin  layer,  on  a  heated  revolv- 
ing drum.  By  this  process  the  evaporation  of  water  takes  place 
rapidly  and  the  dried  film  of  milk  drops,  or  is  scraped,  from  the 
rolls,  appearing  as  a  thin  yellow  scale.  Another  process,  of  re- 
cent date,  consists  of  atomizing  the  milk  under  pressure  into  a 
moving  volume  of  warm  dry  air.  The  moisture  is  instantane- 
ously absorbed  and  by  the  use  of  centrifugal  force,  the  vapor 
charged  air  is  made  to  give  up  the  minute  particles  of  suspended 
matter.  The  product  is  a  fine  flour,  possessing,  in  common,  with 
some  other  brands  prepared  by  other  methods,  the  properties  of 
milk  wThen  again  stirred  up  in  water.  There  are  preparations 
on  the  market  which  do  not  have  these  properties,  probably  be- 
cause they  have  been  subjected  to  too  high  heat  in  the  drying 
process. 

Of  the  several  milk  powders  examined  by  the  authors,  only  one 
contained  any  appreciable  quantity  of  fat.  It  appears  that  most, 
if  not  all  of  these  powders  are  prepared  from  skimmed,  or  par- 
tially skimmed  milk.  This  is  probably  necessary,  in  order  that 
dessication  may  be  more  complete  and  the  keeping  qualities  of 
the  product  well  insured.  One  product  examined,  and  repre- 
sented as  a  preparation  from  whole  milk,  contained  but  9  per 
cent  of  fat.  A  milk  powder  prepared  from  average  whole  milk 
should  contain  at  least  25  per  cent  of  fat. 

Various  other  dry  foods  are  prepared  from  the  casein  of  milk, 


Milk  and  Its  Products  299 

among  which  are  plasmon  and  nutrose.  Plasmon  is  made  by 
treating  the  curd  of  skimmed  milk  with  sodium  bicarbonate  and 
drying  the  thoroughly  mixed  product  in  an  atmosphere  of  car- 
bon-dioxide. Nutrose  is  also  a  sodium  compound  of  casein. 

Cheese.  The  principal  varieties  of  commercial  cheese  are  pre- 
pared from  milk  by  the  action  of  rennet.  Rennet  is  made  by 
extracting  the  fourth  stomach  of  the  calf  with  a  5  to  10  per  cent 
solution  of  common  salt.  Its  power  to  coagulate  milk  is  due  to 
the  presence  of  an  enzyme  called  rennin,  which  plays  a  similar 
part  in  the  process  of  digesting  milk  in  the  calf's  stomach.  Ren- 
nin coagulates  the  casein  of  the  milk,  forming  a  curd  which  me- 
chanically entangles  almost  all  the  fat  of  the  milk,  leaving  the 
albumin  and  sugar  in  the  whey.  Rennin  acts  more  rapidly  at 
about  102  to  104°  F.  In  cold  milk  it  is  slow  in  its  action,  while 
at  temperatures  above  120°  F.  it  is  retarded,  its  action  entirely 
ceasing  at  130°  F.  In  milk  containing  some  acid,  but  not  enough 
to  curdle  it,  rennin  action  is  hastened. 

It  is  impossible  in  a  work  of  this  scope  to  describe  the  varieties 
of  cheese  and  their  methods  of  manufacture. 

The  common  practice  followed  in  the  preparation  of  American 
cheddar  cheese  is  to  "ripen"  the  milk  to  an  acidity  correspond- 
ing to  about  0.25  per  cent  of  lactic  acid.  This  is  done  by  adding 
to  it  a  starter  consisting  of  sour  milk  or  a  pure  culture  of  lactic 
organisms.  The  necessary  rennet  is  then  added,  the  milk  being 
previously  warmed  to  82  to  85°  F.  After  the  curd  is  sufficiently 
firm,  requiring  about  30  minutes,  it  is  cut  into  cubes  and  the 
temperature  of  the  vat  raised  to  100°  F.  It  is  maintained  at 
that  temperature  for  1  to  2  hours,  during  which  time  the  curd 
shrinks  and  the  acidity  increases.  After  proper  acidity  is  de- 
veloped, the  whey  is  drawn,  the  curd  piled  in  one  end  of  the  vat 
and  kept  warm.  In  this  condition  it  mats  into  a  solid  mass.  It 
is  finally  passed  through  a  grinding  mill,  salted,  and  pressed  into 
molds.  The  cheese  is  then  placed  in  a  curing  room  at  a  tem- 
perature of  50  to  60°  F.  and  allowed  to  ripen.  A  lower  tem- 
perature than  this  can  be  used,  with  great  improvement  in  the 


300 


Agricultural  Chemistry 


quality  of  the  product.  In  the  manufacture  of  Swiss  cheese  the 
milk  must  be  in  a  sweet  condition.  No  acid  is  developed  and  the 
curd  is  cooked  at  a  temperature  of  125  to  130°  F.  The  curd  is 
placed  in  molds  and  the  salting  done  by  surface  application.  In 
making  soft  cheese  the  curd  is  not  cut  or  pressed,  but  simply 
allowed  to  drain  on  a  cloth  or  frame. 

Reckoning  that  the  fresh  cheese  which  goes  into  the  cheese 
room  contains  about  36  per.  cent  of  water,  the  products  from  100 
Ibs.  of  normal  milk  will  be  as  follows : — 


Products  from  100  Lbs.  of  Normal  Milk 


Total 
product 

Water 

Protein 

Fat 

Sugar 

Ash 

Milk  

Lbs. 
100.0 

Lbs. 
87.10 

Lbs. 
3.40 

Lbs. 
3.90 

Lbs. 

4.85 

Lbs. 
7.5 

Cheese  

10.40 

3.94 

2.57 

3.59 

0.17 

0.13 

Whey  

89.60 

83.16 

0.83 

0.31 

4.68 

0.62 

Ripening.  Cheddar  cheese  ripens  quickest  at  a  moderately 
warm  temperature,  50  to  60°  F.  being  usually  employed.  It  has 
been  shown  that  it  will  also  ripen  at  a  much  lower  temperature — 
even  at  30°  F. — and  the  product  will  be  of  excellent  quality. 
The  time  of  ripening  is  necessarily  longer  when  conducted  at  the 
lower  temperature.  During  this  curing  process  many  complex 
changes  occur.  The  sugar  is  converted  to  lactic  acid,  some  water 
evaporates,  and  the  insoluble  proteins  are  partly  converted  into 
water  soluble  products.  Ammonium  compounds  are  also  pro- 
duced during  the  ripening  process.  Experiments  have  shown 
that  fresh  cheddar  cheese  contains  but  from  5  to  10  per  cent  of 
its  protein  in  water  soluble  form,  while  at  the  end  of  5  months, 
35  to  40  per  cent  will  be  found  in  that  form.  These  changes,  ac- 
cording to  one  view,  are  produced  primarily  by  the  lactic  acid 
organisms.  Another  theory  ascribes  them  to  enzymatic  action, 
the  enzymes  being  galactase,  which  is  present  in  all  milks  and 


Milk  and  Its  Products 


301 


possesses  the  power  of  peptonizing  casein,  and  pepsin,  contained 
in  the  rennet  extract  used.  Whatever  may  be  the  cause  of  these 
changes,  there  can  be  no  doubt  that  during  the  curing  process  the 
flavor  and  aroma  are  developed  and  that  a  considerable  portion 
of  the  insoluble  nitrogenous  bodies  are  converted  into  water- 
soluble  forms.  The  fat  of  cheese  undergoes  slight  change  during 
ripening,  a  small  proportion  of  the  neutral  fat  being  decomposed 
and  butyric  and  other  fatty  acids  formed.  The  sugar  which  was 
present  when  the  cheese  was  first  made  also  disappears  after  a 
period  of  7  to  10  days.  Lactic  acid  is  the  main  product  formed 
from  the  sugar,  although  other  products,  probably  of  great  im- 
portance to  flavor  development,  are  produced. 

The  ripening  of  special  kinds  of  soft  cheese,  such  as  Roquefort 
and  Camembert  is  attributed  to  such  special  ferments  as  molds, 
introduced  during  the  process  of  manufacture.  The  average 
composition  of  various  cheeses  is  given  in  the  following  table : — 


Composition  of  Cheese 


Water 

Protein 

Fat 

Ash 

Cheddar  

Per  cent 
34.4 

Per  cent 
26.4 

Per  cent 
32.7 

Per  cent 
3.6 

Cheshire  

32.6 

32.5 

26.0 

4.3 

Swiss  

35.8 

24.4 

37.4 

2.4 

Edam  

30.3 

24.1 

30.3 

4.9 

Roquefort  

31.2 

27.6 

33.2 

6.0 

Brie  

50.4 

17.2 

25.1 

5.4 

Liinburg  

35.  6 

28.5 

29.8 

5.9 

Under  the  United  States  pure  food  act,  the  following  defini- 
tions of  cheese  were  established. 

(1)  "Whole  milk  or  full  cream  cheese  is  cheese  made  from  milk 
from  which  no  portion  of  the  fat  has  been  removed. 

(2)  Skim  milk  cheese  is  cheese  made  from  milk  from  which 
any  portion  of  the  fat  has  been  removed. 


302  Agricultural  Chemistry 

(3)  Cream  cheese  is  cheese  made  from  milk  and  cream  or  milk 
containing  not  less  than  6  per  cent  of  fat. 

Standard.  "Whole  milk  or  full  cream  cheese  contains,  in  the 
water-free  substance,  not  less  than  50  per  cent  of  butter  fat. 

The  term  full  cream  simply  means  that  in  the  manufacture, 
whole  milk  has  been  used.  It  gives  the  impression  that  cream 
has  been  added,  but  such  is  not  the  case. 

In  some  cases,  cheese  is  adulterated  by  the  addition  of  foreign 
fat,  as  lard.  Such  cheese  is  usually  known  as  fitted  cheese. 

Whey.  As  already  stated,  whey  contains  almost  all  of  the 
milk  sugar  and  albumin  originally  present  in  the  milk,  as  well 
as  a  portion  of  the  ash.  The  amount  of  fat  in  the  whey  will  de- 
pend upon  the  treatment  the  curd  has  received.  If  the  milk  has 
been  rich,  the  temperature  of  cooking  high,  and  the  curd  roughly 
handled,  considerable  quantities  of  fat  will  be  present.  Where 
whey  is  rich  in  fat,  it  is  customary  to  recover  it  for  the  manu- 
facture of  whey  butter,  either  by  allowing  it  to  rise  by  gravity 
or  through  the  use  of  the  separator.  The  average  composition 
of  whey  is  about  as  follows :  Water,  93.3  per  cent ;  protein,  0.9 ; 
fat,  0.3 ;  sugar,  4.9 ;  ash,  0.6. 

The  cheese  yield  of  milk.  As  has  been  seen,  the  two  milk  con- 
stituents that  must  determine  the  yield  of  cheese  are  casein  and 
fat.  The  percentage  of  these  varies  in  milks  from  different  in- 
dividual cows.  They  are  not  always  in  the  same  relation  in  two 
different  milks.  Milks  of  high  fat  content  are  not  proportionately 
richer  in  casein  than  milks  of  low  fat  content.  As  a  rule,  for  100 
pounds  of  fat  in  Jersey  and  Guernsey  milk,  one  may  expect  55 
to  65  pounds  of  casein,  while  in  the  milk  from  the  Ayrshire  and 
Holstein  breeds,  there  will  be  65  to  75  pounds.  There  will  be 
individual  exceptions  to  this  general  statement. 

In  herd  milks,  although  the  relation  of  casein  to  fat  is  more 
constant,  nevertheless  variations  in  the  proportion  of  these  two 
constituents  exist.  The  general  rule  that  high  fat  milks  do  not 
yield  in  proportion  to  their  fat,  as  much  cheese  as  low  fat  milks, 
finds  its  explanation  in  the  fact  that  high  fat  milks  have  proper- 


Milk  and  Its  Products 


303 


tionately  less  casein.  This  is  illustrated  in  the  following  table, 
which  represents  some  work  done  by  Babcock  at  a  number  of 
Wisconsin  cheese  factories. 


Relation  of  Composition  of  Milk  to  Cheese  Yield 


No.  of 
groups 

No.  of 
reports 

Range 
of  fat 

Average 
per  cent 
of  fat 

Average 
yield   of 
cheese  per 
100  Ibs.  milk 

Lbs.  of 
cured  cheese 
for  1  Ib.  fat 

1 

24 

Under  3.  25 

3.12 

9.19 

2.94 

2 

90 

3.25-3.50 

3.38 

9.28 

2.73 

3 

134 

3.50-3.75 

3.60 

9.40 

2.61 

4 

43 

3.75-4.00 

3.83 

9.80 

2.56     . 

5 

46 

4.00-4.25 

4.09 

10.30 

2.51 

6 

20 

Over  4.  25 

4.44 

10.70 

2.40 

It  will  be  seen  that  the  yield  of  cheese  in  proportion  to  the  fat 
is  less  in  the  rich  milks  than  in  the  poorer  milks.  A  milk  testing 
6  per  cent  of  fat  will  not  make  twice  as  much  cheese  as  one  test- 
ing 3  per  cent. 

Making  out  dividends  at  cheese  factories.  While  the  inequal- 
ity of  the  cheese-yielding  capacity  of  milks,  and  of  the  distribu- 
tion of  dividends,  based  on  their  fat  content  alone,  has  been  rec- 
ognized, it  has  been  quite  generally  asserted  that  such  inequality 
disappeared  because  of  the  improved  quality  of  the  product  made 
from  the  milks  of  higher  fat  content.  This  is  true  when  we  con- 
sider cheese  made  from  skimmed  or  partly  skimmed  milk  and 
from  milk  very  rich  in  fat  or  re-inforced  with  cream.  But  within 
the  range  of  normal  factory  milk  testing  in  fat  from  3  to  4% 
per  cent,  the  quality  of  the  product,  as  judged  by  buyers  for  the 
market,  does  not  show  uniform  improvement  with  increase  o-f  fat 
in  the  milk.  This  has  been  shown  by  the  work  of  the  Canadian 
Experiment  Station  at  Guelph  and  by  the  Wisconsin  Station. 
No  grading  in  the  price  of  cheese,  made  from  normal  whole  milk, 
based  on  its  fat  content,  is  at  present  practiced.  Other  factors, 


304  Agricultural  Chemistry 

as  the  sanitary  condition  of  the  milk  from  which  the  cheese  is 
made  and  the  subsequent  ripening  processes,  play  an  important 
part  in  determining  the  quality  of  the  product. 

Normal  factory  milks  may  vary  in  their  cheese-yielding  capac- 
ity, and  the  quality  of  the  product  from  such  milks  is  not  deter- 
mined by  those  variations  that  may  occur  in  the  fat  and  casein 
content.  It  is  clear  that  the  most  complete  and  equitable  method 
for  the  distribution  of  dividends  at  a  cheese  factory,  is  to  allow 
for  the  amounts  of  both  fat  and  casein  delivered  by  the  patron. 

In  its  simplest  form  this  consists  in  allowing  equal  values  for 
both  the  fat  and  the  casein,  the  amounts  of  which  can  be  deter- 
mined by  methods  applicable  to  factory  conditions.  Such  tests 
are  the  Babcock  fat  test  and  the  mecJianical  casein  test  devised 
by  one  of  the  authors.  A  patron  delivering  100  pounds  of  milk, 
containing  3.5  per  cent  of  fat,  and  2.4  per  cent  of  casein,  should 
be  paid  on  the  basis  of  5.9  pounds  of  cheese  solids  delivered.  The 
price  per  pound  of  cheese  solids  would  be  determined  by  the 
price  received  for  the  cheese  in  the  market. 


CHAPTER  XIII 

INSECTICIDES  AND  RELATED  SUBSTANCES 

A  number  of  miscellanous  substances  used  in  the  agricultural 
industries  depend  primarily  upon  their  chemical  composition  for 
effectiveness.  Prominent  among  these  substances  are  various- 
preparations  for  the  control  or  suppression  of  parasitic  pests 
upon  plants  and  animals  and  the  restriction  of  contagious  dis- 
eases. Brief  consideration  will  be  given  here  to  the  composition, 
and  action  of  the  more  important  of  these  substances.  For  their 
practical  applications,  reference  should  be  made  to  special  books 
and  bulletins  on  these  subjects. 

The  following  classification  of  these  substances  will  be  followed 
for  the  sake  of  order  and  convenience : — 
I.  Insecticides. 
II.  Fungicides. 

III.  Disinfectants,  deodorants  and  antiseptics. 

IV.  Incidental  materials. 

Insecticides  are  substances  used  for  destruction  of  insects, 
feeding  upon  the  fruit,  foliage  or  bark  of  vegetation  and  for  the 
removal  of  ticks  and  similar  pests  from  animals.  These  materials 
have  won  general  recognition  as  essential  factors  in  the  produc- 
tion of  high  grade  fruit. 

They  may  be  classed  as  stomachic,  contact,  or  gaseous  poisons, 
according  to  their  mode  of  action.  Such  insects  as  the  codling 
moth  of  the  apple  and  the  ' '  potato  bug, ' '  which  are  surface  feed- 
ers, may  be  reached  by  poisons  of  the  first  class;  the  aphides  or 
plant  lice  and  other  sucking  insects  must  be  attacked  by  poisons 
of  the  second  class ;  and  the  resistant  scale  insects  and  other  pests 
are  most  efficiently  destroyed  by  fumigation  with  a  poisonous  gas. 

Stomachic  poisons  for  insects  are  generally  dependent  upon 
arsenic  for  their  poisonous  effects.  Arsenic  does  not  enter  these 
substances  as  the  free  element,  but  as  a  constituent  of  white  arse- 
nic, As2O3,  technically  called  arsenious  oxide  or  arsenious  acid. 


306  Agricultural  Chemistry 

Soluble  compounds  of  arsenic  were  at  first  tested  as  insecticides, 
but  they  were  found  to  cause  serious  injury  to  foliage.  Later 
experiments  have  demonstrated  that  arsenical  compounds  insol- 
uble in  water  produced  the  desired  effect,  probably  by  virtue  of 
the  solvent  action  of  the  juices  of  the  digestive  tract  of  the  insect. 
The  resulting  effort  to  furnish  the  arsenic  of  insecticides  in  in- 
soluble form  has  been  stimulated  also  by  the  passage  of  state  laws 
restricting  the  amount  of  arsenic  permissible  in  soluble  form. 

Paris  green  has  been  a  leading  insecticide  in  America  for  over 
fifty  years.  It  was  first  used,  apparently,  in  an  attempt  to  control 
the  Colorado  beetle  or  ' '  potato  bug ' '  which  had  made  its  appear- 
ance in  the  western  United  States.  This  stomachic  poison  contains 
arsenious  acid,  acetic  acid  and  copper  in  a  definite  chemical  struc- 
ture known  as  ' '  Schweinf urt  's  green, ' '  and  technically  known  as 
''copper  aceto-arsenite, "  Cu3(As03)2Cu(C2H302)2-  It  is  pre- 
pared by  adding  a  hot  solution  of  arsenious  oxide  to  a  hot  solu- 
tion of  copper  acetate.  Paris  green  separates  from  the  mixture 
and  settles  out  as  a  rather  fine  powder  of  a  clear,  green  color. 
The  pure  compound  is  practically  insoluble  in  water,  but  readily 
soluble  in  ammonium  hydroxide,  or  ammonia  water,  and  has  the 
following  composition: 

Per  cent 

Copper  oxide,  CuO  31.29 

Arsenious  acid,  AsgO     58.65 

Acetic  acid,  C  H  Q    10.06 

242 

Scorching  of  foliage  by  applications  of  Paris  green  suspended 
in  water  was  frequently  observed  during  its  early  use.  Gillette 
showed,  in  1890,  that  the  use  of  lime  water  or  Bordeaux  mixture 
with  Paris  green  prevented  this  injury.  A  year  later,  Kilgore 
found  that  the  scorching  effects  were  due  to  soluble  forms  of 
arsenic  and  concluded  that  the  preventive  substances  acted  by 
virtue  of  their  lime,  which  fixed  the  soluble  arsenic  in  insoluble 
compounds : — 

As2O3+3Ca  (OH)  2=Ca3  ( AsOJ  2+3H2O 
calcium  arsenite 


Insecticides  and  Related  Substances  307 

Experiments  at  the  New  York  Experiment  Station  with  Paris 
green  and  sodium  arsenite  applied  to  potatoes  led  to  the  conclu- 
sions: "That  Paris  green  is  not  injurious  to  potato  foliage  if  ap- 
plied in  moderate  quantity  with  lime  water  or  Bordeaux  mixture 
evenly  distributed;"  and  "That  sodium  arsenite  should  not  be 
applied  to  potatoes  except  with  Bordeaux  mixture." 

Adulteration  and  the  manufacture  of  impure  Paris  green  were 
more  or  less  prevalent  previous  to  the  passage  of  insecticide  laws. 
Gypsum  or  sulphate  of  lime  was  one  of  the  most  common  adulter- 
ants. This  has  little  if  any  insecticidal  value  and  was  added  to 
increase  the  bulk.  Other  impurities  may  result  from  the  use  of 
crude  materials  or  careless  methods  in  preparation.  Woodworth 
has  given  some  simple  tests  to  detect  common  forms  of  adultera- 
tion. 

The  ammonia  test  is  performed  by  taking  an  amount  of  Paris 
green  that  can  be  held  on  a  five  cent  piece,  transferring  it  to  a 
drinking  glass  and  adding  about  six  tablespoonfuls  of  household 
ammonia  or  "spirits  of  hartshorn."  Keep  the  contents  of  the 
glass  well  stirred  for  five  minutes.  If  the  "green"  is  pure,  it 
will  then  form  a  clear,  dark-blue  solution  and  leave  no  solid 
residue.  If  gypsum  is  present,  it  will  form  a  white  suspension 
in  the  liquid  and  finally  settle  to  the  bottom  of  the  glass.  This 
is  not  a  conclusive  test  since  impurities  soluble  in  ammonia  jnay 
be  present. 

The  glass  test  often  enables  one  to  distinguish  adulterated 
samples  not  detectable  by  ammonia.  Take  such  an  amount  of 
Paris  green  as  can  be  picked  up  readily  on  the  point  of  a  pen 
knife  and  place  it  on  a  small  rectangular  piece  of  clear  glass. 
Holding  the  glass  in  an  inclined  position,  gently  tap  the  lower 
edge  and  the  Paris  green  will  move  down  the  inclined  plane  leav- 
ing a  track  of  dust  behind.  In  the  case  of  a  pure  "green,"  the 
dust  will  be  of  a  bright  green  color.  If  the  sample  is  impure,  it 
may  leave  a  white,  pale-green  or  other-colored  streak,  depending 
upon  the  color  of  the  adulterating  substance.  This  test  is  best 
used  for  comparing  unknown  samples  with  a  sample  known  to  be 


308 


Agricultural  Chemistry 


pure.  Like  the  ammonia  test,  it  is  not  infallible.  Variations 
in  the  color  of  samples  in  bulk,  especially  an  abnormally  pale 
shade,  and  a  tendency  to  dampness  or  lumping,  indicate  almost 
certain  adulteration. 

Microscopic  examination  offers  the  most  certain  and  satisfac- 
tory of  simple  methods  for  testing  the  purity  of  Paris  green. 
The  sample  is  prepared  for  this  test  as  in  the  " glass  test"  just 
described  and  the  dust  is  then  examined  under  a  medium  power 
objective.  The  Paris  green  will  be  seen  in  the  form  of  clean 


On  the  right — pure  Paris-green;  on  the  left — adulterated  Paris-green. 

round  balls;  and  in  perfectly  pure  samples  these  are  all  that  can 
be  seen.  Impure  samples  will  exhibit  also  a  considerable  quan- 
tity of  material  of  crystalline  or  irregular  shapes,  and  usually 
white  in  color.  Excess  of  free  arsenio-us  oxide  is  not  so  readily 
distinguished  by  this  test.  "When  mixed  with  the  prepared  Paris 
green  it  is  as  easily  recognized  by  the  microscope  as  is  any  other 
form  of  adulterant,  but  when  added  in  the  process  of  making,  it 
adheres  firmly  to  the  particles  of  true  green  and  causes  them  to 
stick  together  in  clusters. 

Chemical  analysis  is  the  only  absolute  means  of  determining 
the  purity  of  this  insecticide.     One  of  the  most  important  .of  the 


Insecticides  and  Related  Substances  309 

chemical  determinations  is  that  for  estimating  the  soluble  ar- 
senic in  Paris  green  and  other  insecticides.  Two  procedures  are 
in  use.  In  one  case  the  sample  is  extracted  with  a  hot  33  per  cent 
solution  of  sodium  acetate,  while  in  the  other  case  it  is  extracted 
for  several  days  with  cold  water  and  the  amount  of  arsenic  in 
solution  estimated.  The  former  method  apparently  shows  more 
nearly  the  amount  of  soluble  arsenic  that  may  be  present,  while 
the  latter  treatment  more  nearly  simulates  conditions  to  which 
the  insecticide  is  exposed  in  the  field. 

Control  laws  have  been  passed  by  some  states  to  regulate  the 
composition  and  sale  of  insecticides  as  has  been  done  in  the  case 
of  commercial  fertilizers  and  feeding  stuffs.  In  some  cases,  spe- 
cial stipulation  is  made  with  regard  to  the  amount  of  free  ar- 
senious  oxide  permissible  in  Paris  green.  Idaho  allows  a  max- 
imum amount  of  six  per  cent  for  this  constituent  and  California 
allows  but  four  per  cent.  Purity  and  efficiency  of  insecticides 
can  only  be  insured  by  purchasing  them  under  guarantee  or  un- 
der recommendations  from  reliable  authorities  such  as  the  state 
experiment  stations,  or  by  the  purchase  of  simple  constituents  to 
be  combined  by  the  purchaser. 

Green  arsenoid  is  the  trade  name  for  a  compound  resembling 
Paris  green  in  composition  and  effects.  It  contains  no  acetic 
acid  but  is  formed  from  copper  oxide  and  arsenious  oxide,  and 
is  technically  known  as  copper  arsenite,  CuIIAs03.  The  pure  com- 
pound contains  about  53  per  cent  of  arsenious  oxide,  As2O3.  So- 
dium sulphate  or  Glauber's  salt  Na2SO4  is  a  by-product  in  the 
process  of  preparation  and  may  occur  together  with  sand  and 
other  impurities  in  such  an  insecticide;  they  should,  however, 
be  present  in  only  small  amounts.  The  following  data  from  an 
analysis  of  green  arsenoid  illustrates  the  relative  effect  of  sodium 
acetate  solution  and  cold  water  upon  the  arsenic  of  insecticides : 

Free  arsenious  acid  Per  cent 

(extracted  with  sodium   acetate) 3.23 

(extracted   with   cold    water) 5.88 


310  Agricultural  Chemistry 

This  insecticide  has  given  excellent  results  when  mixed  with 
lime  to  "bind"  the  soluble  arsenious  oxide. 

London  purple  was  imported  from  England  by  Bessey  in  1878 
as  a  substitute  for  Paris  green  in  destroying  the  potato  beetle. 
It  is  prepared  by  boiling  a  purple  residue  from  the  dye  industry, 
containing  free  arsenious  acid,  with  slaked  lime.  Calcium  ar- 
senite  Ca3(AsO3)2  is  formed  at  first,  but  by  subsequent  boiling 
and  exposure  to  the  air,  this  may  be  partly  oxidized  to  calcium 
arsenate,  Ca3(As04)2-f  3H20.  This  insecticide  carries  some  im- 
purities brought  over  from  the  dye-making  process,  and  as  a  re- 
sult of  insufficient  addition  of  lime  or  incomplete  boiling  some 
of  the  arsenious  acid  may  be  present  in  free  condition.  Hay  wood 
examined  four  samples  with  the  following  results: 

Per  cent 

Moisture   1.87-4.07 

Sand  2.46-3.55 

Arsenious  acid,  total 6.40-17.31 

Arsenic  acid,  total 26.50-35.62 

Arsenious  acid,  soluble  in  cold  water 1.44-13.49 

Arsenic  acid,  soluble  in  cold  water 7.12-19. 5C 

Lime  ' 23.59-25.09 

Water  decomposes  both  calcium  arsenate  and  calcium  arsenite 
to  some  extent  and  consequently  a  solubility  determination  with 
water  does  not  show  how  much  arsenious  acid  was  actually  free. 
These  soluble  arsenic  salts  are  probably  less  objectionable  than 
free  arsenious  acid,  although  it  is  recognized  that  London  purple 
is  more  injurious  to  foliage  than  is  Paris  green  and  common 
arsenic  (arsenious  oxide)  is  more  harmful  than  either.  This  con- 
dition may  be  corrected  by  adding  lime  to  the  London  purple 
when  suspending  it  in  water  for  application  to  foliage.  Since 
it  is  subject  to  considerable  variation  in  composition  this  insec- 
ticide should  be  bought  on  guarantee  of  purity. 

Calcium  arsenite  was  proposed  by  Kilgore  as  an  insecticide, 
following  his  observations  with  Paris  green.  This  can  be  made 
by  boiling  one  pound  of  arsenious  oxide  and  two  pounds  of  lime 
in  water  and  diluting  for  use.  Since  this  compound  has  been 


Insecticides  and  Related  Substances  311 

shown  to  form  about  75  per  cent  of  London  purple,  it  is  probably 
more  economical  to  use  the  latter  insecticide. 

Arsenite  of  soda,  Na3As03,  is  prepared  by  boiling  arsenious 
oxide  with  four  times  its  weight  of  sodium  carbonate.  The  in- 
jurious effects  of  this  compound  upon  potato  foliage  have  been 
referred  to.  Similar  results  were  produced  in  trials  of  sodium 
arsenate,  Na3As04,  against  the  gypsy  moth  in  Massachusetts. 

"Dips"  which  have  proved  very  efficient  in  destroying  sheep 
ticks  have  given  sodium  arsenite  recognition  as  a  valuable  in- 
secticide. The  following  formula  has  been  used  with  success: 

Arsenite  of  soda  5  pounds 

Soft  soap  5  pounds 

Aloes  12  ounces 

Water    100  gallons 

The  soap  is  said  to  increase  the  retention  of  the  dip  on  the 
fleece  and  aloes  renders  it  distasteful  to  the  animal  and  prevents 
poisoning.  Sodium  arsenate  has  been  used  against  locusts  by 
adding  it  to  sugared  water  and  spraying  the  grass  in  the  infested 
region. 

Lead  arsenate,  Pb3(As04)2,  was  recommended  as  an  insecti- 
cide in  1892  and  was  first  used  against  tent  caterpillars.  It  is 
prepared  by  adding  lead  acetate  to  sodium  arsenate  in  water. 
These  substances  dissolve  readily  in  the  cold  and  react  to  form 
sodium  acetate  and  neutral  lead  arsenate,  the  latter  remaining 
suspended  as  a  fine  white  powder.  This  insecticide  should  be 
handled  in  the  form  of  a  paste,  for  once  dried  it  is  suspended 
with  difficulty.  Recent  experiments  show  that  when  lead  nitrate 
is  used  in  place  of  the  acetate  in  making  the  arsenate,  the  product 
remains  in  suspension  better  and  contains  more  acid-arsenater 
PbHAs04,  carrying  a  higher  percentage  of  arsenic  than  is  the  case 
with  preparations  from  the  acetate.  The  neutral  arsenate  is  ap- 
parently the  most  insoluble  of  all  the  arsenical  insecticides  and 
least  likely  to  scorch  the  foliage.  Headden  has  shown,  however, 
that  care  should  be  taken  to  use  pure  water  in  the  preparation  of 
even  this  spraying  mixture.  Solutions  of  0.1  per  cent  sodium 
sulphate  or  0.05  per  cent  common  salt  dissolve  considerable 


312  Agricultural  Chemistry 

amounts  of  arsenic  from  lead  arsenate.  Practical  spraying  tests 
with  lead  arsenate  in  distilled  water  showed  that  sodium  carbon- 
ate or  sodium  chloride  at  the  rate  of  10  grains  per  gallon  in  the 
spray  fluid  produced  severe  injury  and  40  grains  of  the  latter 
salt  per  gallon  injured  about  50  per  cent  of  the  foliage.  Salt 
waters  and  alkali  surface  waters  must  therefore  be  avoided. 

Haywood  gives  the  following  directions  for  preparing  lead 
arsenate ;  for  each  pound  of  lead  arsenate  to  be  made,  use — 

Ounces 
Formula  A.     Sodium  arsenate  (65  per  cent) 8 

Lead  acetate  (sugar  of  lead) 22 

Formula  B.     Sodium  arsenate  (65  per  cent) 8 

Lead  nitrate 18 

Dissolve  each  salt  separately  in  1  to  2  gallons  of  water,  using 
wooden  vessels.  When  dissolved,  pour  the  lead  solution  into  the 
sodium  arsenate,  stirring  thoroughly  until  the  mixture  just  turns 
a  potassium-iodide  test  paper  to  a  bright  yellow.  The  lead  salt 
is  then  in  slight  excess.  A  large  excess  should  be  avoided.  Al- 
low the  lead  arsenate  to  settle,  and  pour  off  the  liquid.  These 
chemicals  are  extremely  poisonous  and  should  be  plainly  labeled 
and  handled  with  care. 

Pink  arsenoid  is  a  commercial  preparation  made  by  adding 
lead  acetate  to  sodium  arsenite  and  coloring  the  insoluble  product 
with  a  dye.  It  is  composed  chiefly  of  lead  arsenite,  Pb3(AsO3)2, 
only  a  small  proportion  of  the  arsenic  being  soluble,  and  has 
given  satisfactory  results. 

White  arsenoid  was  the  product  of  an  attempt  to  put  barium 
arsenite,  Ba3(As03)2,  upon  the  market  as  an  insecticide.  Con- 
trary to  expectation,  all  the  arsenious  oxide  of  this  preparation 
was  found  tc  be  soluble  in  cold  water.  It  gave  poor  results  and 
was  short-lived. 

White  arsenic,  or  the  simple  arsenious  oxide,  As203,  has  been 
used  as  a  constituent  of  "dips"  and  various  insect  and  animal 
poisons.  It  is  volatile  at  a  comparatively  low  heat  and  mixed 


Insecticides  and  Belated  Substances  313 

with  sulphur,  it  has  been  successfully  used  against  ants  by  forc- 
ing the  vapors  into  the  nest. 

Arsenical  poisoning  may  occur  in  the  case  of  trees  heavily 
sprayed  with  arsenical  insecticides.  Headden  found  arsenic  in 
diseased  fruit  trees  and  this  condition  was  correlated  with  an 
accumulation  of  arsenic  in  the  soil  in  compounds  from  which  it 
was  rendered  gradually  soluble  by  the  salts  of  the  soil  solution. 
Paige  found,  in  connection  with  reported  poisonings  associated 
with  combating  the  gypsy  moth,  that  the  amount  of  lead  arsenate 
consumed  by  herbivora  with  the  grass  from  beneath  sprayed 
trees  might  lead  to  serious  results.  These  findings  emphasize  the 
need  of  care  in  the  use  of  poisonous  spraying  mixtures. 

Hellebore,  from  the  root  of  the  pokeroot  plant,  and  Pyrethrum 
or  insect  powder,  from  the  flower  heads  of  certain  plants,  have 
poisonous  insecticidal  properties  attributed  to  alkaloids.  Both 
deteriorate  with  age. 

Contact  insecticides  may  act  by  their  caustic  properties  and 
by  absorption  from  the  surface  of  the  insect,  or  by  closing  the 
tracheae  or  breathing  tubes.  These  will  now  receive  our  consid- 
eration. 

Lime-sulphur  wash  is  typical  of  the  former  class  of  insecti- 
cides. It  was  used  in  California  as  a  sheep  dip,  where  it  was  first 
applied  also  to  the  San  Jose  scale  in  1886.  The  wash  was  pre- 
pared by  boiling  sulphur  and  slaked  lime  in  equal  parts,  which 
produced  first  a  simple  sulphide  of 'lime  (CaS)  of  a  white  color. 
Prolonged  boiling  causes  the  color  of  the  wash  to  pass  through 
shades  of  yellow  to  a  deep  orange  color  with  the  formation  of 
poly-sulphides  of  lime  carrying  increasing  proportions  of  sul- 
phur. The  chemistry  of  lime-sulphur  wash  has  been  investigated 
at  the  New  York  Experiment  Station.  The  chief  compounds 
were  found  to  be  calcium  penta-sulphide  (CaS5),  calcium  tetra- 
sulphide  (CaS4)  and  calcium  thiosulphate  (CaS203).  Boiling 
converts  the  last-named  compound  into  calcium  sulphite  CaS03, 
and  free  sulphur,  and  the  calcium  sulphite  then  oxidizes  by  ex- 
posure to  the  air  into  calcium  sulphate,  CaS04 : — 
CaS203+boiling=CaS03-fS 


314  Agricultural  Chemistry 

The  specific  gravity  of  the  wash  and  the  amount  of  calcium 
and  sulphur  in  solution  increased  with  the  amount  of  lime  used. 
The  higher  amounts  of  lime  produced  more  calcium  tetra-sul- 
phide,  while  with  the  smaller  amounts,  the  mixture  was  more 
nearly  penta-sulphide.  The  largest  amount  of  soluble  sulphides 
was  formed  by  boiling  about  one  hour,  especially  when  the  largest 
amount  of  lime  was  used.  The  amount  of  sediment  increased 
with  increased  boiling,  due  to  the  formation  of  calcium  sulphite. 
It  was  found  that  the  addition  of  extra  lime  to  the  diluted  lime- 
sulphur  solution  might  seriously  decrease  its  insecticidal  value 
as  a  result  of  the  decomposition  of  the  higher  sulphides  of  cal- 
cium with  formation  of  free  sulphur.  Where  pure  lime  was  used, 
the  sediment,  found  to  consist  of  calcium  sulphite,  free  sulphur 
and  hydroxide  and  carbonate  of  lime,  formed  suitable  material 
to  add  in  the  making  of  a  new  wash.  It  was  also  found  that  mag- 
nesium oxide  when  present  in  the  lime,  as  in  dolomitic  limestone, 
tended  to  decompose  the  sulphides  of  calcium  with  evolution  of 
hydrogen  sulphide.  The  importance  of  pure  lime  for  this  insec- 
ticide is  thus  emphasized.  An  examination  of  commercial  lime- 
sulphur  preparations  revealed  great  variations  in  composition. 
Since  field  experiments  have  demonstrated  that  this  insecticide 
derives  its  chief  value  from  the  soluble  lime-sulphur  compounds, 
commercial  preparations  should  be  bought  on  the  basis  of  the 
strength  and  composition  of  their  supernatant  liquid. 

The  reactions  involved  in  the  making  and  further  decomposi- 
tion of  lime-sulphur  on  the  tree  may  be  represented  thus : — 

(1)  3Ca(OH)8+6S2=CaS208     +     2CaS5+3H2O 

calcium  calcium 

thio-sulphate   penta  sulphide 

(2)  2CaS5+3O2=2CaS2O3-f3S2 

Stewart  states  that  the  problem  of  making  concentrated  lime- 
sulphur  solutions  is  essentially  one  of  preventing  crystallization 
and  securing  a  storable  product  of  high  density.  He  finds  that 
the  formation  of  crystals  is  largely  due  to  an  excess  of  lime  and 
exposure  to  the  air  when  cold.  Exposure  to  the  air  may  be 


Insecticides  and  Related  Substances  315 

avoided  by  covering  the  surface  of  the  wash  with  oil.  The  in- 
fluence of  materials  sometimes  added  to  increase  the  insecticidal 
effect  has  also  to  be  considered ;  arsenite  of  lime,  as  a  supplemen- 
tary insecticide,  has  been  found  to  produce  least  decomposition 
of  the  sulphur  compounds  of  this  wash. 

Haywood  found  that  a  one  hour  period  of  boiling  dissolved 
practically  all  the  sulphur  used  for  this  wash.  The  addition  of 
common  salt  was  found  to  have  no  effect  so  far  as  the  sulphur  com- 
pounds of  the  wash  were  concerned. 

On  theoretical  grounds,  Haywood  recommends  the  following 
formula  for  preparing,  at  minimum  cost,  a  wash  with  the  max- 
imum amount  of  sulphur  in  solution  and  a  moderate  excess  of 
lime: 

Lime   20-22%  pounds 

Sulphur   20  pounds 

Water  50  gallons 

The  mixture  is  best  when  boiled  by  passing  steam  through  it. 
Moderate  slaking  of  the  lime  was  found  to  have  no  influence,  but 
a  comparison  of  flowers  of  sulphur  and  crystallized  sulphur 
showed  that  the  crystalline  form,  even  when  finely  ground,  re- 
quired much  longer  boiling  for  maximum  solution  and  gave  a 
product  of  variable  composition,  apparently  dependent  on  the 
size  of  the  particles. 

To  determine  what  changes  take  place  after  the  wash  is  ap- 
plied to  trees,  measured  quantities  of  the  clear  liquid  were  ab- 
sorbed on  filter  papers  and  dried  in  the  open  air  exposed  to  sun- 
light. Analyses  at  successive  stages  Stowed  the  gradual  oxida- 
tion of  calcium  penta-sidphide  into  calcium  thiosidphate,  calcium 
sulphite  and  finally  calcium  sulphate,  with  deposition  of  free 
sulpJuir.  Wetting  the  paper  daily  to  simulate  the  daily  wetting 
of  branches  by  dew  greatly  increased  the  rapidity  of  the  process. 
Indications  were,  that  after  four  to  six  months  only  free  sulphur 
and  calcium  sulphate  would  be  left.  Haywood  believes  that  the 
excess  of  caustic  lime  loosens  the  scale  insects  from  the  tree,  and 
that  the  active  agents  in  killing  are  sulphur  in  finely  divided 


316  Agricultural  Chemistry 

form,  thiosulphate,  for  a  time,  and  sulphite,  which  is  gradually 
formed  by  the  slow  oxidations. 

Self  boiled  washes,  in  which  the  heat  for  solution  is  produced 
by  the  chemical  reaction  incident  to  slaking  the  lime,  are  un- 
satisfactory, even  when  a  maximum  amount  of  heat  is  so  gen- 
erated. 

Lime,  sulphur,  salt,  soda-wash,  in  which  caustic  soda  is  used 
in  addition  to  lime,  has  nearly  the  same  composition  and  action 
as  the  simpler  wash  already  described.  It  is  less  effective,  how- 
ever, because  it  decomposes  more  slowly  and  the  sodium  sulphite, 
Na-jSOs,  formed  is  more  subject  to  loss  by  washing  than  is  cal- 
cium sulphite. 

Kerosene  (a  mixture  of  hydrocarbons  of  the  general  formula. 
CnH2n,  standing  between  naphtha  and  paraffine  among  products 
obtained  from  coal  oil)  has  been  used  as  a  contact  insecticide 
against  scale  insects.  It  was  applied  as  a  spray  to  the  dormant 
trees,  but  found  to  be  frequently  injurious.  Applied  to  stag- 
nant pools,  it  effectually  suffocates  the  emerging  pupae  of  mos- 
quitoes; and  in  the  "hopper-dozer"  it  destroys  grasshoppers 
which  are  trapped  in  it,  by  forming  an  oil  film  over  the  tracheae. 

Kerowater  sprays  were  the  result  of  attempts  to  dilute  kero- 
sene before  applying  it  to  trees.  Kerosene  is  not  miscible  with 
water  but  by  forcibly  mixing  these  liquids  at  the  nozzle  of  the 
spray  pump  the  kerosene  was  temporarily  diluted. 

Kerosene  emulsions  are  comparatively  permanent  suspensions 
made  by  mixing  kerosene  oil  with  soap  solutions.  They  are  not 
true  solutions,  for  the  oil  can  be  observed  under  a  microscope  as 
droplets  suspended  in  the  soap  solution.  Well  made  emulsions 
persist  for  several  hours,  and  even  for  days,  and  facilitate  an 
even  distribution  of  the  kerosene.  Crude  petroleum  oils,  which 
are  closely  related  to  kerosene  but  less  volatile  than  the  latter, 
have  taken  its  place  to  a  great  extent  because  of  the  greater 
efficiency  and  safety  attendant  upon  their  use. 

Miscible  oils  are  preparations  of  this  nature.  They  are  based 
on  a  standard  soap  solution  with  which  various  proportions  of 


Insecticides  and  Belated  Substances  317 

different  oils  are  emulsified.  Crude  oil,  a  mixture  of  petroleum 
oils  heavier  than  kerosene;  paraffine  oil,  a  lubricating  oil  from 
petroleum ;  and  resin  oil,  from  the  distillation  of  resin,  are  used. 
The  crude  oils  are  efficient  in  6.6  per  cent  strengths,  whereas 
kerosene  is  inefficient  below  20  per  cent  strength. 

Penny  gives  the  following  formula  for  a  standard  miscible  oil : 

The  "Soap  Solution" 

Menhaden  oil 10  gallons 

Carbolic  acid 8       " 

Caustic  potash 15       " 

Heat  to  290°  or  300°  F.,  then  add  kerosene 2       " 

Water  2 

From  the  above  soap  solution,  the  miscible  oil  is  prepared  ac- 
cording to  the  following  formula: 

Soap  solution   3  %   gallons 

Paraffine  oil 40 

Rosin  oil 6  " 

Water,  as  required  by  test. 

In  the  process  of  making  the  soap  solution  the  kerosene  should 
be  added  while  the  soap  is  hot.  The  heavier  oils  should  be  stirred 
into  the  soap  solution  at  moderate  temperatures.  Freezing  tem- 
peratures should  be  avoided.  The  amount  of  water  to  be  added 
is  a  matter  of  experiment  but  it  should  be  used  in  quantity  suffi- 
cient to  produce  an  emulsion  of  creamy  consistency.  One  gallon 
of  the  soap  solution  or  emulsifier  will  make  8  to  14  gallons  of 
miscible  oil  and  these  8  to  14  gallons  will  make  from  100  to  210 
gallons  of  spray  material,  according  to  dilution. 

Resin  soaps,  efficient  against  orange  scale  insects,  are  prepared 
by  boiling  resin  (consisting  largely  of  abietic  anhydride,  C44H62- 
04,  with  carbonate  of  soda  and  diluting  the  solid  product  with 
water. 

Fish  oil  soap  and  whale  oil  soap,  prepared  by  boiling  the  oils 
in  potash  lye,  K2CO3,  and  diluting  with  water,  are  effective 


318  Agricultural  Chemistry 

against  plant  and  animal  lice,  but  the  commercial  preparations 
are  subject  to  great  variations  in  composition. 

Tobacco  decoction  depends  for  its  value  upon  the  poisonous 
properties  of  nicotine,  C10H14N2.  This  alkaloid  is  soluble  in  wa- 
ter, and  hot  water  extractions  of  the  stalk  and  waste  of  tobacco 
are  used  as  an  insecticide. 

Gaseous  insecticides  are  used  against  insects  particularly  dif- 
ficult to  attack.  Hydrocyanic  acid  gas,  HCN,  is  by  far  the  most 
effective  substance  in  this  class.  It  is  produced  from : — 

Potassium  cyanide,  pure 1  ounce 

Sulphuric  acid,  commercial 2      " 

Water  4      " 

This  is  the  quantity  recommended  for  each  100  cubic  feet  of 
space.  The  cyanide  should  be  added  last,  having  the  mixture  in 
an  earthen-ware  vessel.  Potassium  sulphate  is  formed  and  the 
poisonous  hydrocyanic  acid  is  rapidly  liberated  as  an  invisible 
gas.  This  is  an  extremely  powerful  poison,  a  single  breath  being 
fatal,  and  by  no  means  should  it  be  inhaled  by  the  operator.  To 
retain  the  gas  and  secure  efficient  action,  it  should  be  applied 
in  tightly  closed  rooms  or  buildings,  or  in  tents  specifically  pro- 
vided for  the  purpose,  allowing  it  to  act  for  an  hour  or  more. 
The  enclosure  should  then  be  opened  from  the  outside  and  thor- 
oughly aired  before  being  entered,  and  the  strongly  acid  residue 
from  the  reaction  should  be  carefully  disposed  of. 

Carbon  bisulphide,  CS2  is  a  colorless,  volatile  liquid  formed 
by  passing  sulphur  vapors  over  red  hot  charcoal.  The  gas 
evolved  from  the  liquid  is  heavier  than  air,  inflammable  and  fatal 
to  insects  breathing  it.  Its  chief  use  is  for  the  destruction  of 
weevils  in  grain.  One  teaspoonful  for  each  cubic  foot  of  space 
should  be  placed  in  a  shallow  dish  at  the  surface  of  the  grain, 
and  one  hour  allowed  for  the  evaporation  of  each  teaspoonful 
used.  The  heavy  vapors  sink  through  the  grain  to  the  bottom  of 
the  bin,  where  they  may  be  released  by  boring  holes  through  the 
wall.  Ants,  moles,  prairie  dogs  and  similar  pests  are  extermi- 
nated by  placing  cotton  saturated  with  carbon  bisulphide  in  the 


Insecticides  and  Belated  Substances 


319 


heaps  or  runs  and  covering  tightly.     Carbon  bisulphide  should 
never  be  brought  near  flames. 

Fungicides  are  materials  utilized  for  the  destruction  of  para- 
sitic plants.  Hyposulphite  of  soda,  Na2S2O3,  lime-sulphur  and 
sulphur  alone  were  used  in  this  capacity  as  early  as  1885  against 
apple  scab  and  leaf  blight. 


Note  the  beneficial  results  from  the  control  of  potato  diseases  by  Bor- 
deaux .mixture. 

Bordeaux  mixture  has  been  the  premier  fungicide  since  1883, 
when  Millardet  used  it  against  the  downy  mildew  of  the  grape. 
It  was  accidentally  discovered  by  observing  the  flourishing  con- 
dition of  vines  to  which  lime  and  copper  salts  had  been  applied 
to  prevent  the  theft  of  grapes  in  the  province  of  Bordeaux, 
France.  Several  formulae  have  been  superseded  generally  by 
the  so-called  "normal"  formula,  or  1.6  per  cent  Bordeaux,  which 
consists  of: 

Copper  sulphale,  CuSO4  6  Ibs. 

Quick  lime,  CaO  4  Ibs. 

Water 50  gallons 


320  Agricultural  Chemistry 

The  lime  should  be  slightly  in  excess.  This  may  be  accom- 
plished by  weighing  the  pure  salts  for  the  mixture,  or  by  testing 
the  product. 

The  litmus  test  depends  upon  the  fact  that  so  long  as  copper 
sulphate  is  in  excess  blue  litmus  will  be  turned  red  when  moist- 
ened with  the  Bordeaux  mixture.  Enough  lime  should  be  pres- 
ent so  that  red  litmus  is  turned  blue. 

The  ferro-cyanide  test  may  be  used  also  for  this  purpose.  A 
teaspoonful  of  the  clear  liquid,  obtained  by  straining  if  necessary, 
should  be  added  to  a  few  drops  of  potassium-ferrocyanide  solu- 
tion, K4Fe(CN)6,  in  a  white  porcelain  dish.  A  reddish  brown 
precipitate  or  color,  Cu2Fe(CN)6,  indicates  the  presence  of  solu- 
ble copper  salts,  and  lime  should  be  added  to  the  mixture  until 
this  no  longer  appears. 

The  fungicidal  properties  of  Bordeaux  mixture  are  chiefly  due 
to  the  insoluble  compounds  formed  and  it  is  important  to  keep 
these  thoroughly  in  suspension.  To  facilitate  this,  the  copper 
sulphate  and  lime  should  be  dissolved  separately,  each  in  one-half 
the  water,  and  when  the  lime  is  cool,  they  should  be  poured  to- 
gether with  constant  stirring.  In  this  way,  the  dilute  solutions 
react  to  form  a  fine  suspension  which  will  not  settle  for  several 
hours. 

The  chemistry  of  Bordeaux  mixture  has  been  very  thoroughly 
investigated  by  Pickering  of  the  Woburn  Fruit  Farm,  England. 
It  appears  from  his  work  that  when  lime  is  added  to  copper  sul- 
phate, different  basic  sulphates  are  formed,  depending  upon  the 
proportions  taken  and  that  these  when  sprayed  on  the  tree  are 
decomposed  in  the  air,  forming  copper  carbonate  together  with 
some  copper  sulphate.  It  is  to  the  latter  that  the  fungicidal  ac- 
tion is  to  be  attributed. 

(1)     10  CuSO4+7.5CaO=10  CuO.2.5S03+7.5  CaS04 
(2)    10  Cu0.2.5S03+3.75C02=3.75(CuO)2.C02+2.5CuSO4 

Probably  with  excess  of  lime  a  double  basic  sulphate  of  copper 
and  calcium  is  formed  with  the  composition  CuO.S03.4CaO.SO3. 


Insecticides  and  Related  Substances  321 

Soda  Bordeaux,  made  with  caustic  soda,  NaOH  in  place  of 
lime  in  the  regular  formula,  has  given  satisfactory  results. 

Copper  ammonium  sulphate,  CuS04.4NH3.H20,  a  clear  blue 
solution  formed  from  copper  sulphate  and  ammonia,  also  called 
"eau  celeste,"  has  been  applied  as  a  fungicide,  but  its  caustic 
action  renders  it  unsafe.  Copper  carbonate  dissolved  in  ammonia, 
however,  has  given  good  results.  It  should  be  freshly  prepared, 
as  the  ammonia  may  volatilize  on  standing,  causing  the  copper 
to  fall  out  of  solution. 

Copper  sulphate,  CuS04,  has  been  applied  to  dormant  trees 
and  green-house  plants  as  a  dilute  solution,  but  it  possesses  a 
strongly  acid  reaction  liable  to  injure  the  plant,  and  should  be 
used  with  care.  Smut  on  grains  is  destroyed  by  this  fungicide. 
A  one  to  two  hour  immersion  of  oats  in  a  0.5  to  1.0  per  cent  so- 
lution may  be  safely  practiced,  but  stronger  applications  retard 
germination. 

Potassium  sulphide,  K2S,  is  used  against  mildews  at  the  rate 
of  one-half  ounce  to  one  gallon  of  water.  Concentrated  solutions 
which  are  strongly  alkaline,  are  destructive  to  plants.  Atomic 
sulphur,  which  appears  to  be  a  colloidal  suspension  of  sulphur, 
gives  promise  of  superceding  the  above  sulphide. 

Formalin  or  formaldehyde,  CH20  is  a  most  efficient  agent  for 
destroying  smut  spores  on  grain.  The  seed  should  be  immersed 
for  ten  minutes  in  a  solution  of  1  pint  of  "40  per  cent"  formalin 
to  20  gallons  of  water.  Stronger  solutions  have  been  found  in- 
jurious to  the  germinating  power  of  barley.  The  seed  should 
be  spread  and  finally  mixed  so  as  to  dry  with  not  more  than  two 
to  three  hours  contact  with  the  formalin. 

Disinfectants  are  substances  which  accomplish  the  total  de- 
struction of  the  germs  of  infectious  diseases.  They  may  also  act 
as  deodorants  or  destroyers  of  foul  odors. 

Antiseptics  prevent  decomposition  or  putrefaction  by  arrest- 
ing the  development  of  germs,  but  do  not  necessarily  destroy 
them.  Disinfectants  in  weak  solutions  may  act  as  antiseptics.  Re- 


322  Agricultural  Chemistry 

frigeration,  common  salt  and  sugar,  all  of  which  are  largely  used 
in  preserving  fruits,  meats,  etc.,  are  good  examples  of  antiseptics. 

Formaldehyde  is  perhaps  the  most  commonly  used  chemical 
disinfectant.  It  is  a  product  of  the  oxidation  of  wood  alcohol 
and  is  put  upon  the  market  in  a  38  to  40  per  cent  solution  in 
water.  A  five  per  cent  solution  made  from  this  should  be  mixed 
with  any  solid  matter  to  be  disinfected.  Gaseous  formaldehyde 
is  used  for  disinfecting  inclosed  space  and  porous  solid  matter 
in  bulk.  The  gas  should  be  delivered  into  a  tightly  closed  com- 
partment in  one  of  the  following  ways :  Formalin  may  be  heated 
under  pressure  or  in  a  simple  retort  and  the  gas  piped  into  the 
space;  formalin  may  be  sprayed  upon  sheets  or  other  extensive 
surfaces  in  the  space  to  be  disinfected  and  the  gas  liberated  by 
simple  evaporation;  six  parts  of  formalin  may  be  poured  upon 
five  parts  by  weight  of  chemically  pure  potassium  permanganate. 
In  the  last  case,  heat  is  generated  ~by  the  chemical  reaction  in- 
volved in  the  oxidation  of  the  aldehyde  to  formic  acid  and  50  per 
cent  of  the  formaldehyde  is  liberated  as  a  gas.  Ten  ounces  of 
formalin  are  necessary  for  each  1000  cubic  feet  of  space  in  the 
first  two  cases  and  twice  as  much  must  be  used  in  the  perman- 
ganate method.  This  disinfectant  also  acts  as  a  deodorant. 

Paraform  (CH20)3,  is  a  condensation  product  of  formaldehyde 
put  up  as  a  powder  or  as  pastils.  Two  ounces  of  paraform  liberate 
gas  sufficient  to  disinfect  1000  cubic  feet  of  space. 

Mercuric  chloride  or  corrosive  sublimate,  HgCl2?  is  a  poisonous, 
white,  crystalline  salt.  It  is  usually  put  up  in  tablet  form  with 
ammonium  chloride  to  facilitate  dissolving  in  water.  Strengths 
of  1  to  500  to  1  to  1000  are  used,  the  greater  strength  being  neces- 
sary to  destroy  bacterial  spores.  This  is  a  powerful  stomachic 
poison  and  must  be  handled  with  care.  It  forms  insoluble 
compounds  with  proteins  and  hence  raw  eggs  and  milk  are  given 
as  antidotes.  On  account  of  its  chemical  affinity  for  proteins, 
unless  liberally  used  it  has  little  disinfecting  power  when  applied 
to  excreta,  blood  and  similar  protein  containing  materials.  Solu- 


Insecticides  and  Related  Substances  323 

tions  of  this  salt  should  be  used  only  in  glass  or  earthen  ware, 
as  it  reacts  with  tin  and  other  common  metals. 

Chloride  of  lime  (bleaching  powder),  CaCl(OCl),  is  both  a 
disinfectant  and  deodorizer,  acting  as  an  oxidizing  agent  by  vir- 
tue of  the  chlorine  which  it  liberates.  It  is  prepared  by  passing 
chlorine  gas  over  slaked  lime.  The  compound  decomposes  rapidly 
on  exposure  to  the  air  and  hence  is  put  up  in  hermetically  sealed 
containers  and  is  reliable  only  when  freshly  removed  from  these. 

Carbolic  acid,  C6H5OH,  is  a  derivative  of  benzene,  C6H0,  a 
hydrocarbon  wrhich  forms  the  basis  of  the  coal  tar  dyes.  At  or- 
dinary temperatures  it  has  the  crystalline  form  of  long,  white 
needles.  One  part  of  water  to  9  parts  of  the  crystals  produces  a 
liquid,  in  which  form  it  is  commonly  dispensed.  By  dissolving 
in  warm  water  a  solution  of  slightly  over  6  per  cent  carbolic  acid 
can  be  made.  This  is  used  as  a  spray  and  wash.  Cresol  or  crude 
carbolic  acid  is  a  crude  preparation  from  coal  tar  distillation,  the 
latter  substance  being  the  liquid  by-product  in  the  production  of 
gas  and  coke  from  coal.  This  disinfectant  is  a  mixture  of  var- 
ious coal  tar  oils  and  so-called  cresylic  acids  or  cresols  and  con- 
tains little  or  no  true  carbolic  acid.  Its  disinfecting  power  is 
due  to  the  cresols,  compounds  related  to  carbolic  acid  but  more 
efficient,  and  a  2  per  cent  solution  of  these  is  considered  superior 
to  a  5  per  cent  solution  of  the  latter.  Grades  of  crude  carbolic 
acid  containing  less  than  90  per  cent  of  cresols  are  undesirable, 
because  of  the  lowered  solubility  of  the  latter  by  oils  usually 
present  as  impurities.  The  undissolved  cresols  that  are  present 
necessitate  a  thorough  mixing  while  spraying  in  order  to  facili- 
tate an  even  distribution  of  the  material. 

Cresol  (trikresol),  C6H4(CH3)OH,  is  supplied  to  the  trade 
from  the  coal  tar  industry  in  varying  degrees  of  purity.  It  con- 
tains bodies  of  the  same  general  composition,  but  which  are  su- 
perior to  carbolic  acid  as  disinfectants. 

These  coal  tar  compounds  are  the  basis  also  of  a  number  of 
commercial,  soluble  disinfectants  and  dips,  such  as  creolin,  lysol, 
solveol,  car-sul  dip,  carboleum,  cresol,  disinfectall,  germol, 


324  Agricultural  Chemistry 

and  zenoleum.  Fly  removers,  applied  to  animals  for  protection 
against  flies,  have  been  prepared  from  these  substances.  Light 
coal  tar  oil  for  this  purpose  has  given  the  most  satisfaction  as 
to  persistence  and  freedom  from  gumming  on  the  animal's  coat. 

Creosote  preparations  for  antiseptic  treatment  of  timbers 
against  bacteria  and  fungi  are  the  heavier  fractions  of  coal  tar 
oil  and  carry  carbolic  acid,  the  cresols,  naphthalene,  C10H8  (also 
used  in  moth  balls),  anthracene,  C14H10,  and  similar  high-boil- 
ing hydrocarbons  and  carbolic-acid-like  bodies. 

Deodorants  include  some  of  the  above  materials,  such  as 
chloride  of  lime,  which  destroy  the  causal  substance  through 
chemical  action.  Other  substances  merely  cover  up  the  offensive 
odor  by  the  odor  they  themselves  produce.  Charcoal  (C) ,  is  a  de- 
odorant by  virtue  of  its  great  absorptive  capacity  for  gases.  It 
acts  by  mechanical  absorption  of  offensive  gases  into  its  pores. 

Incidental  materials.  Use  is  often  made  of  arsenite  of  soda, 
common  salt,  carbolic  acid,  sulphuric  acid  and  other  compounds, 
as  weed  destroyers.  Iron  sulphate  solution,  prepared  by  dissolv- 
ing 100  pounds  of  the  granulated  salt  in  50  gallons  of  water  for 
each  acre  of  land,  has  been  successfully  used  in  eradicating  wild 
mustard.  Untoward  effects  of  these  substances  on  the  soil  can 
be  corrected  in  many  cases  by  applications  of  lime,  which  proba- 
bly reacts  with  them  to  form  neutral  or  insoluble  compounds.  . 


APPENDIX 


COMPOSITION  OF  SOILS 

Snyder  gives  the  following  average  composition  of  200  fertile 
soils;  analysis  was  made  by  strong  hydrochloric  acid  (Sp.  gr. 
1.115). 

Insoluble  matter  79.95  Per  cent. 

Potash  0.29  " 

Soda 0.25  " 

Lime 2.16  " 

Magnesia 0.55  "       " 

Iron  oxide 2.68  " 

Alumina   5.20  " 

Phosphoric  acid  0.24  " 

Sulphur  trioxide  0.03  " 

Carbon  dioxide 1.12  " 

Volatile  matter  .  7.00  " 


99.47 
Volatile  matter  containing: 

Humus 3.35 

Nitrogen  29 


326  Agricultural  Chemistry 

FERTILIZING  CONSTITUENTS   OF  FEEDING  STUFFS. 
Fertilizing  Constituents  in  One  Ton  of  Material 


Feed 

N 
Nitrogen 
Ibs. 

P208 
Phosphoric 
acid,  Ibs. 

K2O 
Potash 
Ibs. 

Dry  matter 
Ibs. 

Concentrates 
Corn  

36.4 

14.0 

8.0 

1,764 

Corn  bran  

32.6 

24.2 

13.6 

1,818 

Hominy  chops  

32.6 

19.6 

9.8 

Gl  uten  feed  

76.8 

8.2 

0.6 

1,  844 

Wheat  

47.2 

15.8 

10.0 

1,732 

Wheat  middling.:!  

52.6 

19.0 

12.6 

1,748 

Rye  

35.2 

16.4 

10.8 

1,714 

Barley  

30.2 

15.8 

9.6 

1,714 

Malt  sprouts  

71.0 

28.6 

32.6 

1,760 

Brewers'  grains  (dried  )  

72.4 

20.6 

1.8 

1,810 

Oat  feed  

34.4 

18.2 

10.6 

1,734 

Cotton  seed  meal  

13.5 

57.6 

17.4 

1,823 

Peas  

61.6 

16.4 

19.8 

1,720 

Roughage 
Corn  stover  

20.8 

5.8 

28.0 

1,816 

Timothy  hay  

25.2 

10.6 

18.0 

1,726 

Red  clover  hay  (medium)  

41.4 

7.6 

44.0 

1,684 

Red  clover  hay  (mammoth)  .  .  . 
Crimson  clover  hay  

44.6 
41.0 

11.0 
8.0 

24.4 

26.2 

1,772 
1,672 

Alfalfa  hav  

43.8 

10.2 

33.6 

1,850 

Silage 
Corn  

5.6 

2.2 

7.4 

441 

Straw 
Oat  

12.4 

4.0 

24.8 

1,710 

Barlev  

26.2 

6.0 

41.8 

1,716 

Roots  and  Tubers 
Potatoes  

6.4 

2.4 

9.2 

500 

Beet,  common  

4.8 

1.8 

8.8 

245 

Beet,  sugar  

4.4 

2.0 

9.6 

360 

Rutabaga   

3.8 

2.4 

9.8 

218 

Turnip  

3.6 

2.0 

7.8 

184 

Miscellaneous 
Cabbage  

7.6 

2.2 

8.6 

220 

9.0 

3.0 

7.2 

290 

Appendix 


327 


COMPOSITION  OF  FERTILIZERS 

Composition  of  fertilizer  materials  supplying  nitrogen 


Per  cent 
Nitrogen 

Per  cent 
Phosphoric 
acid 

Per  cent 
Potash 

Nitrate  of  soda                

15.5-16 

19    -20.5 

Dried  blood  (high  grade)                     

12    -14 

Concentrated  tankage                      

11    -12.5 

1-2 

Tankage  (  bone)  .  .  .  .  ,  •  

5-6 

11  -  14 

Nitrogenous  guano  

3-7 

9-19 

2-4 

Composition  of  fertilizer  materials  supplying  phosphoric  acid 


Per  cent 
Phosphoric 
acid 

Per  cent 
Nitrogen 

S  Carolina  rock  (ground)  (floats)    

25  -  30 

S.  Carolina  rock  (dissolved)  

12  -  16 

Florida  rock     .           ...               

25  -  30 

Thomas  slag  

18  -  23 

Ground  bone  

20  -  25 

2.5  -  4.5 

Steamed  bone  

22  -  29 

1.5  -  2.5 

Bone  black  ... 

32  -  36 

Composition  of  fertilizer  materials  supplying  potash 


Muriate  of  potash  (80-85  per  cent  pure)  .... 

Per  cent 
Potash 

50  -  53 

Per  cent 
Nitrogen 

Per  cent 
Phosphoric 
acid 

Sulphate  of  potash  (high  grade)  

48  -  52 

Sulphate  of  potash  (low  grade)  

28  -  30 

12  -  13 

3-8 

2-3 

3-5 

\Vood  ashes  

4-8 

1-2 

Agricultural  Chemistry 


COMPOSITION  OF  FEEDING  STUFFS 

The  following  brief  table  gives  the  composition  of  some  typical 
feeding  materials  (taken  from  "The  Feeding  of  Animals,"  Jor- 
dan, Appendix)  : 


«a 

•-  ~ 

-28 
c3 

*l 

A 

o 

a 
|i 

^§5 
P. 

Crude  Protein 
per  cent 

I* 

fe  g 

is. 

s  ^ 

0 

Nitrogen-free 
extract  per  cent 

Ether  extract 
per  cent 

FODDERS 
Corn  fodder  (green)  

79.3 

1.2 

1.8 

5.0 

12.2 

.5 

"        "      (field  cured)  

42.2 

2.7 

4.5 

14.3 

34.7 

1.6 

Corn  silage  

79.1 

1.4 

1.7 

6.0 

11.0 

.8 

Timothy  (green)  .  .  .  

61.6 

2.1 

3.1 

11.8 

20.2 

1.2 

"           hay     

13.2 

4.4 

5.9 

29.0 

45.0 

2.5 

Alfalfa  (green  )  

71.8 

2.7 

4.8 

7.4 

12.3 

1.0 

'  '        hay  

8.4 

7.4 

14.3 

25.0 

42.7 

2.2 

Clover  hay  (red)  

15.3 

6.2 

12.3 

24.8 

38.1 

3.3 

Boors 

90.5 

.8 

1.1 

1.2 

6.2 

.2 

Rutabagas  

88.6 

1.2 

1.2 

1.3 

7.5 

.2 

GRAINS 
Corn  

10.9 

1.5 

10.5 

2.1 

69.6 

5.4 

10.9 

2.4 

12.4 

2.7 

69.8 

1.8 

Oats  

11.0 

3.0 

11.8 

9.5 

59.7 

5.0 

Wheat  

10.5 

1.8 

11.9 

1.8 

71.9 

2.1 

MILL  PRODUCTS 
Corn  meal  

15.0 

1.4 

9.2 

1.9 

68.7 

3.8 

Corn  and  cob  meal  

15.1 

1.5 

8.5 

6.6 

64.8 

3.5 

Wheat  flour    

12.4 

.5 

10.8 

2 

75.0 

1.1 

Wheat  bran  

11.9 

5.8 

15.4 

9.0 

53.9 

4.0 

Gluten  feed  

7.8 

1.1 

24.0 

5.3 

51.2 

10.6 

Oat  feed  

7.7 

3.7 

16.0 

6.1 

59.4 

7.1 

Brewers'  grains  (dried)  

8.2 

3.6 

19.9 

11.0 

51.7 

5.6 

Linseed  meal  (new  process)  
Malt  sprouts  

10.0 
5.0 

5.2 
6.4 

36.1 
27.6 

8.4 
10.9 

36.7 
47.1 

3.6 
3-0 

Appendix 


329 


AVERAGE  COEFFICIENTS  OF  DIGESTIBILITY 

A  brief  table  giving  the  coefficients  of  digestibility  of  important  feed- 
ing materials.    Taken  from  the  "Feeding  of  Animals"  (Jordan). 

Digestion  by  Ruminants 


Feed 

S-t 

—  fl 

l» 

P   a 

Organic 
matter 
per  cent 

4> 
IK    W 

•<3  fc. 

0) 

& 

c 
"°  § 

<D   - 

-2S, 
c 
o 

43 

**    § 

s  % 

p. 

^  w"! 

&£•*-*    . 

ox  £ 

Ether  extract 
per  cent 

FODDERS 
Corn  fodder  (green)  
(field  cured) 
Corn  silage  

67.8 
68.2 
70.8 

69.8 
70.7 
73.6 

35.6 
30.6 
30.3 

59.7 
56.1 
56.0 

60.2 
65.8 
70.0 

73.7 

72.7 
76.1 

74.1 
73.9 

82.4 

Timothy  (green)  

63.5 

65.6 

32.2 

48.1 

55.6 

65.7 

53.1 

hay  

56.6 

57.9 

32.8 

46.9 

52  5 

62.3 

52.2 

Alfalfa  (green)         .    . 

67  0 

64  0 

81.0 

41  0 

72.0 

45.0 

"      hay  

58.9 

60.7 

39.5 

72.0 

46.0 

69.2 

51.0 

ROOTS 
Turnips  

92.8 

96.1 

58.6 

89.7 

103.0 

96.5 

87.5 

Rutabagas  

87.2 

91  1 

31.2 

80.3 

74.2 

94.7 

84.2 

GRAINS 
Corn  
Barley  

89.4 

89.6 
86  0 

67.9 
70  0 

58.0 
50.0 

94.6 
92.0 

92.1 

89.0 

Oat  

71.0 

78  0 

26  0 

77.0 

83.0 

MILL  PRODUCTS 
Corn  meal  

89  4 

89  6 

67.9 

94.6 

92.1 

Corn  and  cob  meal  

78.7 

79  8 

55  6 

45.7 

87.6 

84.1 

Wheat  bran  . 

62  3 

65  7 

77  8 

28  6 

69  4 

68  0 

Gluten  feed  . 

86  3 

87  3 

85  6 

78  0 

89  2 

84.4 

Oat  feed  

62.0 

65  3 

81.1 

42  6 

67.4 

89.0 

Brewers'  grains  (dried)  .  . 

61.6 

65.4 

79.3 

52.6 

57.8 

91.1 

Linseed  ineal   (new  pro- 
cess)   
Malt  sprouts  .  . 

79.2 
67.1 

81.8 
67.2 

85.2 
80.2 

80.4 
32.9 

86.1 
68.1 

96.6 
104.6 

Digestion  by  Horses 


Timothy  (  hay)  

43.5 

44.1 

34.0 

Alfalfa  (hay)  
Oat  (grain)  
Barley  "  
Corn  " 

'ss'.i' 

58.0 
69.0 
87.0 
89.0 

21.2 
73.0 
79.0 
80.0 
75.6 


42.6 
40.0 
29.0 

46'.  6' 


47.3 
70.0 
75.0 
87.0 
95.7 


Digestion  by  Swine 


Barlev  

80.1 

80.3 

5.4 

81  4 

48  7 

86  6 

57  0 

Corn  (unground)  

89.7 

91.3 

89  9 

48  7 

93  9 

77  6 

Corn  (finely  ground)  

89.5 

91.2 

86.1 

29  4 

94  2 

81  7 

Corn  and  cob  meal  

75.6 

76.7 

75.7 

28.5 

83  6 

82  0 

Wheat  (unground)  

72.0 

44.0 

70.0 

30  0 

74  0 

60  0 

Wheat  (cracked  )  
bran  
Lirseed  mpal   

82.0 
65.8 
77  5 

50.0 
10  0 

80.0 
75.1 

86  0 

60.0 
33.0 
12  0 

83.0 
65.5 
85  0 

70.0 

71.8 
80  0 

330 


Agricultural  Chemistry 


WOLFF'S  FEEDING  STANDARDS 

Per  day  per  1,000  ibs.  live  weight 


Kind  of  animal 

Total 
dry 
matter 

Digestible  organic  matter 

Nutritive 
ratio  1: 

Protein 

Carbo- 
hydrates 

Fat 

1.     Oxen 
At  rest  

Lbs. 

18 
22 
25 

28 

30 
30 
26 

25 
29 

20 
23 
25 

30 

28 

20 
26 
22 

36 
32 
25 

Lbs. 
0.7 
1.4 
2.0 

2.8 

2.5 
3.0 
2.7 

1.6 
2.5 

1.2 
1.5 

2.9 

3.0 
3.5 

1.5 
2.5 
2.5 

4.5 
4.0 

2.7 

Lbs. 
8.0 
10.0 
11.5 
13.0 

15.0 
14.5 
15.0 

10.0 
13.0 

10.5 
12.0 
15.0 

15.0 
14.5 

9.5 

13.3 
15.5 

25.0 
24.0 
18.0 

Lbs. 
0.1 
0.3 
0.5 
0.8 

0.5 
0.7 
0.7 

0.3 
0.5 

0.2 
0.3 
0.5 

0.5 
0.6 

0.4 
0.8 
0.4 

0.7 
0.5 
0.4 

11.8 
7.7 
6.5 
5.3 

6.5 
5.4 

6.2 

6.7 
5.7 

9.1 

8.5 
5.6 

5.4 
4.5 

7.0 

6.0 
6.6 

5.9 
6.3 
7.0 

Light  work  

Moderate  work  

Severe  work  

2.    Fattening  bovines 
First  period  

Second  period  

Third  period  

3.     Milch  cows 
Daily  milk  yield  11  Ibs. 
Daily  milk  yield  22  Ibs. 
4.     Sheep 
Coarse  wool  

Fine  wool  

Ewes,  suckling  lambs.. 
Fattening  sheep 
First  period  

Second  period  

5.     Horses 
Light  work  

Heavy  work  

6.     Brood  sows  

7.     Fattening  swine 
First  period  

Second  period  

Third  period      

Appendix. 


331 


WOLFF'S  FEEDING  STANDARDS  (Continued). 


Kind  of  animal 
Age  in  months 

Live 
weight 
per 
head 

Total 
dry 
matter 

Digestible  organic  matter 

Nutritive 
ratio  1  : 

Protein 

Carbo- 
hydrates 

Fat 

Growing  cattle 
DAIRY  BREEDS 
2-3  

Lbs. 

150 

300 
500 
700 
900 

165 

330 
550 
750 
935 

60 
75 
85 
90 
100 

65 
85 
100 
120 
150 

45 
100 
120 
175 
260 

45 
110 
150 
200 
275 

Lbs. 

23 

24 
27 
26 
26 

23 
24 
25 
24 
24 

25 
25 
23 
22 

22 

26 
26 
24 
23 
22 

44 
35 
32 
28 
25 

44 
35 
33 
30 

26 

Lbs. 

4.0 
3.0 
2.0 
1.8 
1.5 

4.2 
3.5 
2.5 
2.0 
1.8 

3.4 
2.8 
2.1 
1.8 
1.5 

4.4 
3.5 
3.0 
2.2 

2.0 

7.6 
5.0 
3.7 
2.8 
2.1 

7.6 
5.0 
4.3 
3.6 
3.0 

Lbs. 

13.0 
12.8 
12.5 
12.5 
12.0 

13.0 
12.8 
13.2 
12.5 
12.0 

15.4 

13.8 
11.5 
11.2 
10.8 

15.5 

15.0 
14.3 
12.6 
12.0 

28.0 
23.1 
21.3 
18.7 
15.3 

28.0 
23  .  1 
22.3 
20.5 
18.3 

Lbs. 

2.0 
1.0 
0.5 
0.4 
0.3 

2.0 
1.5 
0.7 
0.5 
0.4 

0.7 
0.6 
0.5 
0.4 
0.3 

0.9 
0,7 
0.5 
0.5 
0.4 

1.0 
0.8 
0.4 
0.3 
0..2 

1.0 
0.8 
0.6 
0.4 
0.3 

4.5 
5.1 

6.  a 

7.5 

8.5 

:      4.2 
4.7 
6.0 
6.8 
7.2 

5.0 
5.4 
6.0 
7.0 

7.7 

4.0 

4.S 
5.2 

6.  a 

6.5 

4.0 
5.0 
6.0 
7-0 

7.5 

4.0 
5.0 
5.5 
6.O 
6.4 

3_G                

6-12  

12-18  

18-24  

BEEF  BREEDS 
2-3         

3-6         

6-12     

12-1  <  

18-24               

Growing  sheep 
WOOL  BREEDS 
4-6  

6-8  

8-11  

11-15  

15-20     

MUTTON  BREEDS 
4-6  

6-8     

8-11  

11-15  

15-20  

Growing  swine 
BREEDING  STOCK 
2-3  

3-5  

5-6  

6-8  

8-12  

Growing  Fattening 
Animals 
2-3  

3-5  

5-6  

6-8  

8-12  

332  Agricultural  Chemistry 

PRODUCTION  VALUES  PER  100  POUNDS. 

A  table  giving  the  production  value  of  feeds  for  fattening  pur- 
poses.    Computed  according  to  Kellner. 


Feeding  Stuff 

Total 
dry 
matter 

Total 
Crude 
Fiber 

Digestible 

Production 
Value 
Therms 

d 
'S 

1 
fi 

OB 

.    cu 

|2 
*r° 
3$ 

4a 

« 
fc 

Green  Fodder  and  Silage: 
Alfalfa  

Lbs. 
28.2 
29.2 
20.7 
25.6 
28.9 
23.4 
38.4 

91.6 

84.7 
57.8 
59.5 
89.3 
92.3 
84.0 
88.7 
86.8 

90.8 
92.9 
90.4 

11.4 
9.1 
21.1 
9.5 

89.1 
89.1 
84.9 
89.0 
88.4 
89.5 

24.3 
91.8 
91.9 
91.8 

90.8 
90.1 
89.8 

88.2 
88.5 

Lbs. 
7.4 
8.1 
5.0 
5.8 
9.2 
11.6 
11.8 

25.0 
24.8 
14.3 
19.7 
20.1 
27.7 
27.2 
22.3 
29.6 

37.0 
88.  9 
38.1 

1.3 
0.8 
0.6 
1.2 

2.7 
2.1 
6.6 
9.5 
1.7 
1.8 

3.8 
5.6 
6.4 
6.1 

8.9 
8.8 
10.7 
3  3 
9^0 

Lbs. 
2.50 
2.21 
0.41 
1.21 
1.33 
1.44 
1.04 

6.93 
5.41 
2.13 
1.80 
8.57 
3.00 
2.59 
7.68 
2.05 

1.09 
0.63 
0.37 

0.37 
0.14 
0.45 
0.22 

8.37 
6.79 
4.53 
8.36 
8.12 
8.90 

3.81 
35.15 
19.95 
21.56 

27.53 
29.26 
12.36 
11.35 
10.21 

Lbs. 
11.20 
14.82 
12.08 
14.57 
15.63 
14.11 
21.22 

37.33 
38.15 
32.34 
33.16 
38.40 
51.67 
33.35 
38.72 
43.72 

38.64 
40.58 
36.30 

7.83 
5.65 
16.43 
6.46 

64.83 
66.12 
60.06 
48.34 
69.73 
69.21 

9.37 
16.52 
54.22 
43.02 

32.81 
38.72 
43.50 
52.40 
41.23 

Lbs. 
0.41 
0.69 
0.37 
0.88 
0.36 
0.44 
0.64 

1.38 
1.81 
1.15 
0.57 
1.51 
1.34 
1.67 
1.54 
1.43 

0.76 
0.38 
0.40 

0.22 
0.11 

10.80 
14.52 
11.02 
14.26 
13.14 
10.31 
17.80 

34.41 
34.73 
30-53 
26.53 
42.76 
44.03 
36.97 
38.65 
33.56 

21.21 

20.87 
16.56 

7.82 
4.62 
18.05 
5.74 

80.75 
88.84 
72.05 
66.27 
81.72 
82.63 

14.82 
84.20 
79.32 
85.46 

78.92 
74.67 
46.33 
56.65 
48.23 

Clover  —Red  

Corn  Fodder  

"    Silage  

Hungarian  Grass  

Rye   

Timothy  

Hay  and  Dry  Coarse  Fodders: 
Alfalfa  Hav  

Clover  Hay  —  Red  

Corn  Fodder  (field  cured)  — 
"    Stover  

Cow  Pea  Hay  

Hungarian  Hay  

Oat  Hay  

Soy  Bean  Hay  

Timothy  Hay  

Straws: 
Oat  

Rye  

Wheat  

Roots,  etc.  :  

Carrots  

Mangel  -wurzels  

Potatoes  

Turnips  

0.11 

1.60 
4.97 
2.94 
4.18 
1.36 
1.68 

1.38 
12.58 
5.35 
11.87 

7.06 
2.90 
1.16 
1.79 

2.87 

Grains: 
Barley  

Corn  

Corn  and  Cob  Meal  

Oat  .         

Rye  

Wheat  

By  Products: 
Brewers'  Grains  —  wet  

Cottonseed  Meal  1  ... 

Gluten  Feed  —  dry  

"       Meal,  Buffalo  

Linseed-meal: 
Old  Process  

New      "      

Malt  Sprouts  

Rye  Bran  

Wheat  Bran  

Appendix. 


333 


CO  CO 

35         CO  GO 

CD        35  Tfi 

eo      ic  >c 

o      S5O  -r 

WHIS 

Oc€ 

CO         rH  CO 
35        r-i  >C 

co      o:  ic 

"O        T—  i  CO 

1C        O  CO 
CO               CM 

g    S^2 

l-HTf 

1C        1C  CO 

rH          1C  rH 

CO        CM  Tt< 

CO        CD  CC  ?0 

nuoiqo 

0<N 

ex,      oeo 

Tt«          O  CO 

CO         O  rH 

I-H           Tf  C5  —  1 
rH         t"» 

CX|  C5 

rH          O  t- 

t^          OTf< 

T»*             OO 

o      eo  35  cs 

ppB  ouoqdsoqj 

Tf   CO 

N           S^ 

O          CO  CD 

C5         O  GO 

CO        CM  Tfi  OS 

rH          i-l  CM  CO 

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INDEX 


ABOMASUM,  230. 
Acid,  definition  of,  16. 
Acids,  organic  in  plants,  106. 
Adult  animal,  264. 
Aerobic  organisms,  136. 
Agrosterol,  50. 
Albite,  38. 
Albumin,  definition  of,  107. 

in  plants,  108. 

in  animals,  216. 

in  milk,  282. 
Albuminoids,  definition  of,  216. 

in  animals,  216. 
Alinit,  64. 
Alkali,  "black,"  83. 

tolerance  of  plant  to,  83. 

"white,"  83. 

Aluminum  in  plants,  116. 
Alkaloids,  110. 
Amides,  in  plants,  109. 

in  animals,  218. 
Amines,  in  plants,  110. 
Amino-acids,  in  plants,  109. 

in  animals,  218. 
Ammonia,  in  the  air,  33. 

in  water,  33. 

loss  from  manure,  135. 
Ammonification,  61. 
Ammonium  sulphate,  157. 
Amylopsin,  233. 
Anaerobic  organisms,  136. 
Animal,  constituents,  216. 

manure,  119. 

action  on  soil,  45. 

composition  of  bodies,  219. 
Antiseptics,  321. 

in  milk,  290. 


Ants,  in  soil  formation,  46. 

Apples,  203. 

Apatite,  40. 

Arginine,  50,  109. 

Argon,  32. 

Armsby's  feeding  standards,  254. 

Arsenic,  as  insecticide,  305. 

Artificial  manures,  155. 

Ash,  in  animal  products,  220. 

in  feeds,  21,  111,  228. 

importance  to  animals,  228. 
Assimilation  of  carbon  dioxide,  92. 
Ass'  milk,  289. 
Atmosphere,  24. 
Atomic  sulphur,  321. 
Available  pnosphoric  acid  in  fer- 
tilizers, 164. 

energy,  248. 
Avenin,  269. 
Ayrshire  milk,  285,  291. 
Azotobacter,  64. 

BACTERIA,   action   in   digestion, 
235. 

action  in  milk,  289. 

assimilation  of  nitrogen,  29. 
Barium,  in  plants,  117. 
Barley,  grain  composition,  191. 

straw  composition,  193. 
Base,  definition  of,  16. 
Basic  slag,  166. 
Beans,  grain  composition,  196. 

field,  196. 

soy,  196. 
Beets,  202. 
Bile,  233. 
Bleaching  powders,  323. 


338 


Index 


Blood,  221. 

dried  for  manure,  160. 
Boiler  scale,  78. 
Bone  ash,  166. 
Bones,  166,  222. 
Boracic  acid,  290. 
Bordeaux  mixture,  319. 
Bran,  wheat,  190. 
Bran,  corn,  195. 
Brewer's  grains,  193. 
Bromine,  117. 
Buckwheat,  197. 
Butter,  294. 
Butter  milk,  296. 

CABBAGE,  204. 

Calcium,  function  in  plants,  113. 

occurrence,  12. 

carbonate,  39. 

in  soils,  41. 

cyanamide,  159. 

nitrate,  159. 
Caliche,  158. 
Calf,  composition,  219. 
Calorie,  definition,  8. 
Camphors,  105. 
Cane  sugar,  96. 
Capillarity,  57. 
Carbohydrates,  in  plants,  95. 

in  animals,  218. 

function  in  animals,  227. 
Carbolic  acid,  323. 
Carbon,  occurrence,  9. 

dioxide  in  air,  32. 

assimilation,  92. 

in  decay,  51. 

respiratory,  236. 

in  soil  gases,  65. 

as  a  solvent,  46. 
Carbon  bisulphide,  318. 
Carcass,  composition  of,  219. 

in  increase,  221. 


Cartilage,  224. 
Casein,  282. 
Castor  bean,  198. 

oil,  198. 
Cellulose,  99. 
Cereals,  182. 
Chalk,  41. 
Cheese,  299. 

Chemical  changes  in  soil,  59. 
Chemical  manures,  155. 
Chili  saltpeter,  158. 
Chlorine,  bleaching  action,  15. 

as  a  disinfectant,  323. 

function  in  plants,  115. 

occurrence,  14. 
Chlorophyll,  92. 
Churning,  294. 

Clay,  occurrence  and  composition, 
.39. 

physical  and  chemical  proper- 
ties, 48. 

Climate,  influence  oil  plants,  209. 
Clovers,  199. 
Collagen,  224. 
Colloids,  57. 
Colostrum,  260. 
Cooking  food,  242. 
Combustion,  spontaneous,  103. 
Condensed  milk,  297. 
Connecting  tissue,  224. 
Constituents  of  plants,  17,  22. 
Copper  sulphate,  321. 
Corn,  composition,  193. 

stover,  148. 
'silage,  200. 
Cotton  seed  meal,  161,  196. 

oil,  196. 
Cow,  digestion  in,  230. 

ration  for,  274. 
Cream,  291. 
Creosote,  324. 
Creatin,  237. 


Index 


339 


Creatinin,  237. 

Cresol,  323. 

Crops,  classification,  182. 

residues,  189. 
Crude  fiber  of  feeds,  184. 
Cytosine,  50. 

DAIRY,  278. 
Denitrification,  63,  137. 
Dent  corn,  194. 
Dextrine,  98. 
Dextrose,  95. 
Diastase,  85. 
Diffusion  in  soils,  56. 
Digestibility  of  feeds,  241. 
Digestion,  228. 

coeflBcient  of,  239. 

energy  consumed  in,  249. 
Dips,  323. 
Disinfectants,  321. 
Dissolved  bones,  166. 

phosphate  rock,  163. 
Dolomite,  39. 
Drainage,  65. 

EGGS,  220. 

Elastin,  224. 

Elements,  7. 

Elimination  from  animal,  237. 

Energy,  lost  in  digestion,  248. 

utilized  in  labor,  267. 
Ensilage,  200. 
Enzymes,  85,  229. 
Erepsin,  234. 
Essential  oils,  105. 
Ether  extract  of  foods,  185,  246. 
Evaporation,  from  plants,  91. 

soil,  58. 

Ewe's  milk,  260. 
Excretion,  in  animals,  237. 

in  plants,  89. 

FALLOW,  58. 
Farmyard  manure,  118. 


composition,  120. 

decomposition  of,  135. 

preservation  of,  138. 

relation  to  fertility,  147. 
Fat,  digestion  of,  234. 

heat  producing  value  of,  226. 

in  animal  body,  223. 

in  feeds,  102. 

of  milk,  280. 

Fat  globules  in  milk,  281. 
Fats,  nature  of,  103. 
Fatty  acids,  saturated,  102. 

unsaturated,  102. 
Fat  production,  from  proteins,  276. 

from  carbohydrates,  276. 

starch  equivalent,  252. 
Fattening  animals,  269. 

rations,  270. 
Feathers,  216. 
Feeding  standards,  239. 
Feldspars,  38. 
Fermentation,  of  manure,  135. 

in  silo,  201. 
Fertilizers,  155. 

complete,  156. 

laws,  180. 

selection  of,  175. 
Flax,  197. 
Flowers,  93. 
Fluorine,  216. 
Fodder  crops,  198. 
Food  constituents,  function  of,  225. 

composition,  184. 

digestibility,  241. 

economy  of,  275. 

influence  on  butter,  286. 

influence  on  milk,  286. 

manurial  value,  122. 

production  value,  250. 
Formaldehyde,  322. 
Frost,  action  of,  44. 
Fruits,  203. 


340 


Index 


Fuel  value,  animal  products,  8. 

food  constituents,  247. 
Fumigation,  318. 

tobacco,  318. 
Fungi,  319. 
Fungicides,  319. 

GALACTASE,  300. 

Galactaus,  99. 

Galactose,  96. 

Gases,  in  soil,  65. 

Gastric  juice,  230. 

Germination,  of  seeds,  85. 

Glaciers,  action  of,  42. 

Globulins,  107. 

Glucose,  95. 

Glutamin,  110. 

Glycerine,  102. 

Glycogen,  218. 

Goats,  digestion  in,  241. 

Grapes,  83. 

Grasses,  composition,  199. 

digestibility,  241. 
Green  arsenoid,  309. 
Green  manuring,  152. 
Gravel,  57. 
Grits,  41. 
Guano,  bat,  167. 

fish,  167. 
Gypsum,  172. 

HAEMOGLOBIN,  222. 
Hair,  161. 

Hardness,  of  water,  76. 
Hay  crop,  199. 

composition,  200. 

digestibility  of,  205. 
Heat,  of  animal,  265. 

of  combustion,  8. 

relation  to  plant,  93. 

relation  to  soil,  52. 
Hellebore,  313. 


Hemp  seed,  197. 
Histidine,  50,  109. 
Hoof  meal,  161. 
Horn  meal,  161. 
Horse,  digestion  in,  230. 

labor  ration,  267. 

manure,  120. 
Humus,  function  in  soil,  49. 

physical  properties,  52. 
Hydrated  silicates,  39,  40. 
Hydrates  of  iron  and  aluminum, 

39. 

Hydrocyanic  acid,  318. 
Hydrogen,  occurrence,  9. 
Hypoxanthine,  50. 

IGNEOUS  ROCKS,  37. 

Increase,  while  fattening,  221. 

Indian  corn,  193. 

Insecticides,  305. 

Iodine,  116. 

Iron,  function  in  plant,  115. 

in  soils,  38. 

occurrence,  14. 

pyrites,  40. 
Irrigation  waters,  82. 

JERSEY  MILK,  285,  291. 

KAINIT,  169. 
Keratin,  224. 

LABOR  RATION,  267. 

Labradorite,  38. 

Lactic  acid,  in  milk,  289. 

in  silage,  201. 
Lactose,  282. 
Lead,  action  of  water  on,  79. 

arsenate,  311. 
Leaves,  function  of,  91. 
Leather,  161. 
Lecithin;  104. 


Index 


341 


Leguminous  crops,  200. 

Leucine,  109. 

Lentils,  271. 

Levulose,  96. 

Light,  action  on  plants,  92. 

Lignin,  100. 

Lignoceric  acid,  50. 

Lime,  as  a  manure,  170. 

in  foods,  277. 

in  soils,  42. 
Limestone,  49. 
Limonite,  40. 
Linseed,  197. 
Lipase,  86,  233. 
Litter,  125. 
Loco-weed,  117. 
London  purple,  310. 
Lupines,  154. 
Lysol,  323. 

MAGNESIUM,  functions  of,  113. 
occurrence,  14. 
silicates,  39. 

Maintenance  ration,  264. 
Maltose,   97. 
Malt,  192. 
Malts  prouts,  192. 
Mangels,  202. 
Manure,  farmyard,  118. 
application,  144. 
composition,  120. 
decomposition,  135. 
yield  by  animals,  121. 
Manurial  value  of  feeds,  122. 
Maple  sap,  96. 
Marl,  48. 

Marrow  of  bones,  222. 
Margarine,  296. 
Meadow  hay,  199. 
Metamorphic  rocks,  37. 
Methane,  production  in  digestion, 
248. 


Mica,  38. 

Milk,  albumin,  282. 

ash,  283. 

cows,  285. 

composition  of,  284. 

fat  of,  280. 

physical  properties,  284. 

powders,  297. 

preservation,  289. 

souring,  289. 

sugar,  282. 

of  various  animals,  289. 
Milking  cows,  rations  for,  274. 
Mineral  phosphates,  162. 
Minerals,  38. 

Miscellaneous  materials,  324. 
Muscular  tissue,  223. 
Muriate  of  potash,  168. 

NITRATE,  OF  POTASH,  158. 

of  soda,  158. 
Nitrates,  conservation  of,  137. 

loss  by  drainage,  6£ 

produced  in  soil,  62. 
Nitric  acid,  in  air,  32. 

in  rain,  33. 
Nitrification,  61. 
Nitro-bacter,  29. 
Nitrogen,  in  air,  29. 

assimilation,  29. 

fixation,  29. 

occurrence,  10. 

stored  up,  by  animals,  217. 
by  plants,  213. 

voided  by  animals,  226. 
Nodules  on  legumes,  47. 
Nucleins,  107. 
Nucleic  acid,  107. 
Nutrition,  of  animals,  224. 

of  plants,  18. 
Nutritive  ratio,  244. 


342 


Index 


OAT,  GRAIN,  193. 

hay,  199. 

straw,  193. 
Oil  meal,  197. 
Oils,  influence  on  milk  fat,  287. 

drying  and  non-drying,  103. 

essential,  105. 

nature  of,  105. 
Oleic  acid,  102. 
Olein,  103. 
Oleomargarine,  296. 
Omasum,  230. 

Organic  acids  in  plants,  106. 
Orthoclase,  38. 
Oxidation,  16. 
slow,  103. 

Oxen,  ration  for  fattening,  269. 
ash  stored  up,  123. 
comparison  with  cow,  275. 
Oxygen,  in  the  air,  31. 

occurrence,  7. 
Ozone,  32. 

PALMITIN,  103. 
Pancreatic  juice,  233. 
Pace,    influence   on    food   require- 
ment, 267. 
Paraffinic  acid,  50. 
Pasteurizing,  290. 
Paris  green,  306. 
Pears,  203. 
Peas,  196. 
Peat,  125. 
Pectins,  101. 
Pentosans,  101. 
Pentoses,  101. 
Pepsin,  231. 
Peptones,  216. 
Perspiration,  237. 
Petroleum  emulsion,  316. 
Phosphates,  loss  by  drainage,  69. 
Phosphatic  fertilizers,  162. 


Phosphorus,    function    in    plants, 
114. 

occurrence,  12. 

in  animals,  220. 

in  foods,  228. 
Phytin,  117. 
Phytosterol,  50. 
Pigs,  ration  for  fattening,  271. 

rations  for  growing,  259. 

manure  of,  120. 
Pink  arsenoid,  312. 
Plants,  assimilation,  92. 

constituents,  94. 

respiration,  93. 
Plums,  203. 
Pop  corn,  194. 
Potash,  loss  in  drainage,  69. 

fertilizers,  167. 
Potassium,  function  in  plants,  114. 

occurrence,  13. 
Potassium  nitrate,  158. 
Potatoes,  203. 
Preservation  of  milk,  289. 
"Process"  butter,  296. 
Proteins,  classification,  107. 

kinds  of,  108. 
Ptyalin,  230. 
Putrefaction,  17. 

QUARTZ,  38. 
Quick  lime,  171. 

RAFFINOSE,  97. 

Rain  water,  75. 

Rape,  198. 

Rechnagel's  phenomenon,  284. 

Reduction,  16. 

Rennin,  231. 

Rennet,  299. 

Renovated  butter,  295. 

Resins,  106. 

Resin  soap,  as  insecticide,  317. 


Index 


343 


Respiration,  in  animals,  236. 

in  plants,  93. 
Reticulum,  230. 
Reverted  phosphates,  163. 
Rice,  195. 
Ripening,  of  cheese,  300. 

cream,  295. 
River  water,  81. 
Rocks,  classification  of,  37. 
Root,  crops,  202. 

pressure,  89. 
Rotation  of  crops,  211. 
Ruminants,  digestion  by,  241. 
Rye,  191. 

SALICYLIC  ACID,  290. 
Saliva,  229. 
Salt,  common,  172. 
Sand,  properties  of,  48. 
Schweinfurth's  green,  306. 
Sea  water,  84. 

Season,  influence  on  plant  compo- 
sition, 209. 

Seeds,  germination,  85. 
Sedimentary  rocks,  37. 
Selenite,  40. 
Separated  milk,  293 
Sewage  as  manure,  82. 
Shales,  41. 
Sheep,  nutritive  ratio  for,  272. 

digestion  of  foods,  241. 

manure,  120. 

production  of  wool,  273. 
Silage,  corn,  200. 

clover,    200. 
Silicon,  function  in  plants,  115. 

occurrence,  15. 
Silicates  in  soil,  39. 
Size  of  animal,  influence  on  ration, 

265. 

Skimmed  milk,  293. 
Soap,  action  on  hard  water,  76. 

nature  of,  104. 


Sodium,  occurrence,  13. 
Softening  of  hard  water,  77. 
Soils,  composition  of,  70. 

definition  of,  37. 

fixation  of  nitrogen  in,  64. 

formation,  43. 

gases  in,  65. 

potential  food  in,  72. 

retention  by,  60. 

source  of  plant  food,  69. 
Soil,    sedentary   and   transported, 
42. 

relation  to  heat,  52. 

relation  to  water,  55. 

tenacity  of,  54. 

water  in,  54. 

weight  per  acre,  69. 
Sorghum,  200. 
Specific  heat,  51. 
Spontaneous  combustion,  103. 
Starch,  in  plants,  97. 

influence  on  digestion,  243. 

part  in  nutrition,  227. 

production  value,  252. 
Steapsin,  233. 
Stems  of  plants,  89. 
Stearin,  102. 
Sterilization,  290. 
Stomata  of  plants,  91. 
Stomach,  digestion  in,  230. 
Straw  as  litter,  125. 

energy  consumed  in  digestion 

of,  248. 
Sucrose,  96. 
Sugar  beets,  202. 
Sugars,  96. 
Suint,  273. 

Sulphate  of  ammonia,  157. 
Sulphur,  function  in  plants,  115. 

occurrence,  11. 
Sulphur  and  lime  wash,  31S. 

dioxide,  34. 
Sunflower,  198. 


Index 


Super-phosphates,  163. 
Swede,  crop,  202. 
Sweet  corn,  211. 

TEMPERATURE  OF  SOILS,  52. 

Terpenes,  105. 

Therms,  247. 

Thomas  slag,  166. 

Tillage,  65. 

Timber,  composition  of,  188. 

Tobacco,  204. 

as  fertilizer,  170. 
Transpiration  from  leaves,  91. 
Trees,  food  requirements,  204. 
Trypsin,  233. 

Tubercles  on  legumes,  30. 
Turnips,  202. 

UREA,  237. 
Uric  acid,  237. 
Urine,  237. 

VETCHES,  214. 

Ville  fertilizer  system,  175. 


WAGNER      FERTILIZER 

TEM,  176. 
Warp  soils,  82. 
Water,  action  of  on  lead,  79. 

action  of  on  rocks,  43. 

hard,  76. 

mineral,  75. 


SYS- 


natural,  74. 

organic  matter  in,  79. 

physical  properties  of,  74. 

rain,  75. 

soft,  75. 

spring,  75. 

typical  good  and  bad,  80. 
Waxes,  104. 
Wheat,  189. 
Wheat  bran,  190. 
Wheat  straw,  191. 
Whey,  302. 
Whey  butter,  302. 
White  ants,  46. 
White  arsenic,  312. 
White  arsenoid,  312. 
Wind,  action  on  rocks,  43. 
Wolff's  feeding  standards,  245. 
Wood  ashes,  170. 
Wool,  production,  272. 
Woolen  waste,  161. 
Work,  production  of,  267. 
Worms,  in  soil  formation,  45. 

XANTHIN,  50,  223. 

YOLK,  of  wool,  273. 

Young  animals,  nutrition  of,  259. 

ZEIN,  108. 

Zeolites,  40. 

Zinc,  in  plants,  116. 


UNIVERSITY  OF  CALIFORNIA  AT  LOS  ANGELES 

THE  UNIVERSITY  LIBRARY 
This  book  is  DUE  on  the  last  date  stamped  below 


JAN  8     1943 


Form  L-9 
10m -3,' 


S585 
H25g 


